1) No prob, like i mentioned, I just put them in on a whim, not sure how they'll turn out myself. Blackberries can work. With that said, most domesticated cultivars call for full sun. All the wild ones I ever find here grow under trees and in edge environments though, something a guild emulates. So I see no reason why they wouldn't, they may just produce a few less berries depending on how much they're shaded. Be careful to keep them from clumping up too much or they can get out of hand, just the tip of a shoot touching ground and you'll get a new plant (not really a bad thing). I'd look for an erect, thornless variety otherwise you'll have to provide support for the canes. Beyond that theres yearly maintenance cutting away dead canes which will overwinter pests if you leave them, easy enough to tell, just cut away the brown, brittle ones. You can also buy primocane or floricane varieties. Primocan will fruit on first year canes, floricane will produce on second year canes. Really a personal preference but there may be a bit a variety in berry quality. Primocane tend to produce a first year crop a of little different quality than the canes second year crop.
2) Not sure how the seaberries stack with nitro fixing. For that matter I'm also not sure if any studies have been done that compare the two. With that said, the amound of nitrogen fixed will vary and I doubt theres a scientific way to quantify it. Nitro fixing also depends on the variety you choose having the proper symbiotic bacteria in the soil (the guys that fix the nitrogen in the first place). When you buy your nitrogen fixers look for an inoculant or a "nitro-coating" both provide the right bacteria. Keep in mind seaberries have fairly healthy thorns on them. The variety I bought (leikora or star of altai, can't remember) get about 8ft tall. They also need a male plant to produce berries, so you'll need at least two. Autumn Olive or Goumi are also other options that fix nitro. I've given the reasons I chose goumi over autumn olive, but I threw both seaberry and goumi in the mix. Not sure if you have any black walnuts on the property (they're everywhere here) but goumi and autumn olive can both grow near/under walnut
3) That I'm unsure of, don't have any particular experience with borage. I've went the variety route with my bee attractants. Beyond the myriad flowering plants I've sowed a large portion of my field in wildflowers (an annual/perinneal mix I bought at Lowes), in addition to clover already on site, and various other landscaping flowers I have throughout the place. The way I see it, its a "build it and they will come" philosophy. This is honestly my first growing season with everything, so I'm waiting to see how it plays out. If it doesn't work I hope to get a hive in the future anyway, and since I've still got 3 years before anything really starts to bear I should have time to get it figured out.
4) The clover depends. Red clover is biennial, be reseeds easily. White clover (what most people think of) is perennial. I'm unsure about yellow clover. White spreads by rhizomes and will fill an area in nicely and if you buy the right strains will stay at a nice low height (maybe 8"). Red clover, which farmers plant in pastures around here gets taller (maybe 1.5 feet) and has more of an upright plant growth, versus spreading across the ground. Personally I'd go with white (dutch white being popular). It'll probably spread into the grass some, depending on the thickness of the grass anyway, but it's not a bad thing. Most of my "lawn" is actually clover lol…but it wasn't exactly cared for and manicured by the previous owner (I found an above-ground swimming pool, and random car parts buried in my back yard lol). Most commercial lawn mixes add a bit of clover as it's just good for the grass. Once again, make sure you buy the nitrocoated clovers. Maybe not necessary, but it'll insure you get nitro-fixation going.
5) Truth be told, on the insect repellant thing I'm not really sure. Keep in mind they just "repel" they don't "stop". A bug hungry enough will just plow on through anyway. They only really repel bugs from themselves, they just help "mask" other plants. Think mosquitos and citronella, yeah it technically repels them, but I bet you've been bit while hiding behind a protective barrier of citronella candles and torches before too. I personally find the "repellant" claims a bit optimistic myself. My bug strategy once again (like my bee strategy) relies on variety. I've got a mix of plants beneficials love, I let some areas in my back field grow wild (habitat), I've placed feeders out to encourage birds in the area for a dayshift patrol, and I'm putting out a
bat house to hopefully bring in a nightshift patrol. Given the proper variety of habitat nature should see to itself and balance the problem out. Naturally though, you have to have a few pests to bring predators, its more about keeping things at an acceptable level.
Pretty sure I've listed nothing but perennials (don't want to skim back through lol) as that was my focus as well. I'm not to keen on having to constantly plant, so I've skipped over annuals as well unless they easily selfseed or bring something to the table I can't get elsewhere.