Tom Bexley

Congrats on pulling it off. An old house, a big tree, knotweed and a Michigan basement sounds like you managed to buy yourself a whole hobby along with the house
If it were mine I'd probably make a boring priority list before getting sucked into the fun projects: anything involving water first, then roof, then anything that could fall on the house, then the rest. Old houses seem to have a way of making the cosmetic stuff look urgent while the unexciting stuff is what actually saves money later.

Borrowing tools from neighbors seems like one that's fading too. There used to be less expectation that every house needed its own copy of every tool.
You knew who had the post hole digger, who had the trailer, who had the good ladder, and sooner or later they borrowed something from you. Probably saved everybody money and gave people a reason to actually know each other.

The mushroom powder comment caught my attention. I've seen it mentioned a few times as a way to add some depth without making the dish taste obviously like mushrooms. Another one I keep seeing is a little unsweetened cocoa in chili. Not enough to make it taste like chocolate, just enough to darken the flavor a bit. Has anyone here tried that?

If you want to know whether the ants are involved I wouldn't worry too much about the number of nests in the yard. Watch the actual tree. Look at the trunk and main branches for 5 or 10 minutes when its warm and the ants are active. If they're tending aphids you will usually see workers moving up and down the same route and spending time right around the aphid colonies. I'd also look underneath the curled leaves. The ants can be pretty easy to miss from a few feet away, especially on a small tree.
The thing is, if there are tons of ants in the yard but no traffic going up the plum, I wouldn't blame them for the aphid problem without some more evidence.

The insect question would make me a little more cautious about leaving the bales exposed. I don't know that straw itself would be especially attractive to carpenter ants, but gaps between bales are another story. Ants don't always need to excavate something to use it, sometimes an existing void is good enough. And if there is wood framing nearby that stays damp you've given them an even better place. I'd probably be more concerned with keeping the wall dry and eliminating easy entry points than trying to make the straw itself insect proof. A good plaster coat with the bottom and openings detailed well seems like cheap insurance.

Fire ants are a different animal of course, but I wouldnt assume “ants haven't bothered my bales yet” means insects never will.

I wouldnt assume the Douglas fir 1/4 mile away is where the ants in the house are coming from. They can have satellite nests too, sometimes right in or around the structure.Since you're seeing them around the window and door jamb, I'd probably start there. Look for any old water damage, soft wood, failed caulk, condensation, anything that stays damp. Another thing that might help is going outside after dark with a flashlight and watching where they actually travel. If you find a steady trail, follow it in both directions if you can. That can tell you a lot more than trying to guess where the nest is. Also keep an eye out for coarse sawdust or little piles of debris around trim, siding, windows etc. Carpenter ants sometimes push that stuff out of the nest and it can give away where they're working. Personally I'd try to figure out if there is a nest in the house first before worrying too much about making a barrier outside.

Interesting observation about the pink foam versus the white expanded foam. One thing worth mentioning is that carpenter ants aren't actually eating the foam any more than they eat wood. They excavate it to make galleries and nesting space.So if someone finds tunnels in foamboard, I wouldn't assume the inslation itself attracted them as food. I would look around the edges and behind it for an access route, nearbyy damp wood, or an existing place the ants are using as a nest. Keeping the lower edge of the insulation protected and inspectable seems like a good idea, especially where it meets soil or wood.The little piles of foam particles they kick out can also be a useful clue that something is excavating inside where you can't see it.

One thing I would add is to decide whether you are trying to repel the ants or get them to carry bait back to the colony. Doing both at the same time can work against you. If I were using bait, I would leave their trail alone for a few days and put the bait right alongside it. Let the workers find it and keep returning. Once activity stops, then clean the trails and work on sealing the entry points.I would also try to identify the ants before doing much else. If they are fairly large ants, especially if you notice them more at night, I would check around the sink, dishwasher, windows and any other damp areas. Carpenter ants often turn up where there is moisture-damaged wood, and fixing the moisture problem is more important long term than simply making the visible ants disappear.