Thanks for the additional information. I am still wondering what your goals are for the property? Are you deriving the bulk of your income from farm activities? Are the sheep a hobby or part of a business?
Without knowing what your goals are or what the site actually looks like (some kind of base map), it is difficult to speak directly.
Still, if I may offer some advice:
1) Spend time this winter figuring out what you would like to do on the property and whether or not it is feasible. Divide the property into
permaculture zones of use with specific strategies for each and how they may or may not interact with one another.
2) Come to terms with the scale of the property and apply your time,
energy, and resources towards implementing mainframe
permaculture design issues revolving around water, access, and soil. I cannot emphasize enough how much of a boon passive water harvesting features are on a property. I also cannot emphasize enough how important it is that you pay close attention to access. Avoiding soil compaction through well planned access is paramount towards shifting your property towards a forest ecosystem.
3) Determine where you can intervene with the highest chance of success with the least effort, especially when it comes to paying attention to design details that improve the situation for the entire site.
4) I would focus on wind breaks. Instead of trucking around compost, manure, and soil amendments to the entire site and everyone getting a little bit (which decreases its effectiveness), focus on promoting design features. Wind breaks for the entire site are of paramount importance. If those get established, everything they
shelter will grow better regardless of whether or not you can spare fertilizer for them or not. As your site is large, it will take some effort to determine which windbreaks are top priority. Still, develop some kind of hierarchy of which features are going to get the bulk of your attention. Focusing on fundamental design issues is going to reap the most rewards. That doesn't mean stop observing the entire site, but it does mean that spreading yourself thin just isn't going to achieve what you want.
5) Once you have focused on your wind breaks, I would recommend researching and becoming thoroughly familiar with Holistic Management (developed by
Allan Savory). HM is its own holistic design process that is complimentary to
permaculture, but is an independent, stand on its own idea. Develop a plan for managing your property and putting your sheep to use throughout the land to distribute that manure. If your sheep are receiving some kind of mineral supplement, it is possible that some of those trace minerals will make their way to the topsoil between your tree rows. You live in an ideal location for this kind of work.
6) You mention wanting to inoculate your soil with forest organisms, especially fungi. This is a good idea, especially if coupled with a clear cut plan on which patches of your property you are going to focus your attention on. One way to bring forest soil life into the system is to bring clean, fresh
wood chips into a healthy forest where you have permission to do this. Layer the wood chips underneath the fresh leaf litter and mark the area somehow so you can remember where your substrate is. Come back in a year, in late fall (or even the following spring, you want at least one autumn to pass), and check the patch. The wood chips should be clearly bound together with fungal mycelium, and probably some roots. You can then take your now inoculated substrate back to your trees. If you have located the substrate under specific trees that match the ones you want to encourage, this could work better. Be warned that there is no telling exactly what species of organisms you are now trucking back to your land! This can just as easily bring undesirable organisms, but on balance, beneficial ones should outnumber the undesirable ones. Additionally, most of these fungi will be of the decomposer variety. There may or may not be some mycorrhizal fungi in there.
For transport, make sure that the substrate stays moist (but not drowning) and when you bring it to your land, that you immediately put it into contact with the soil and cover with a solid layer of mulch to protect the organisms from the elements.
Note: research about mycorrhizal fungi and what they do and what they don't do. There is a lot of misinformation from companies as well as good intentioned, but misinformed talk out there about how to promote them. Here are a few tips to get started: Never (I rarely use that word) spray mycorrhizal fungi on plants. They are obligate species. In all but rare occurrences, they need to be in direct contact with a symbiotic partner in order to grow and survive. Remove a mycorrhizal fungi from its partner species and it will die. They don't live on leaves. They live in the soil. The Rodale Institute has an "on farm guide" to producing your own endomycorrhizal fungi inoculant. It would be worth a look since they partner with the vast majority of species. Learn about how the disperse themselves (read: you cannot propagate them in compost or in compost teas) On the other hand, many of the trees you have planted will associate with ectomycorrhizal fungi. Research which ones, which species, and see about ordering some. Inoculate certain trees that will put ectomycorrhizal
mushrooms upwind of the rest of your property and target species during their fruiting months to facilitate their spread throughout the property.
7) If you can, bring dead wood into the property. Not only wood chips, but logs of all sizes. Put them in direct contact with the soil. You don't have to build
hugel mounds if you don't want to (although they could be very useful). If you can put logs into direct contact with the soil within a reasonable distance of the specific tree patches you are targeting, within a few years their roots will go into the logs and begin to
milk the log for water and nutrients. Additionally, mycorrhizal fungi will go into the log and do the same. If the log is mulched so that it doesn't dry out as easily, then you are on your way. Do that a few dozen times around the trees you really need to get going for your windbreak and you have a cheap and effective
boost to the soil life. Wood chips are great, but they are relatively expensive and decompose quickly. What you want to do is act like a forest.
8#) Another way you can do that is to take branches and do soil staking- simply staking branches into the soil near the trees to facilitate the soil life.
9) If herbivores are a problem in your area, find out how you can facilitate predation. Are there any locations that are suitable for raptors to nest? Is there standing (but not necessarily stagnant) water available on site for foxes and such? The bog you mentioned could be seen as a focal point in enticing the entire food chain to play a part on your property, depending on its relative location to the other features and locations on the property.
These recommendations rest upon the knowledge that the trees, shrubs, other plants and life on your property know what they are doing. As the designer, as the organism on site that can use tools and plan, it is our obligation (IMO) to play to those strengths. Help your plants help themselves and they will do the rest. Hope that helps!
edit- Tried to fix some of the typos. The rest will just have to stay unfixed.