I went back to Home Depot this afternoon.
The sales rep in the flooring department did not seem to know what she was talking about, and was not even really fluent in English. She mostly kept suggesting that I come back tomorrow to talk to the manager who has the most experience. She also seemed to suggest I should rip everything up, level it again, and do a floating install, even though I kept repeating that I did not have enough material for that, could not afford it, and that the middle 10 feet of floor looks perfect as is.
When I mentioned the wood filler I have she went and got a smaller tube of the brand they sell and said it could be used for repairs, but had nothing really useful to add.
She seemed impressed by how well I managed to get the transition strip stained to match the floor boards, but then went on to try to sell some alternative strips that would not work in my situation.
I ended up just buying the 1 gallon container of engineered hardwood glue and ignoring everything she said.
When I returned the trim boards that were not big enough to cover all the bad spots on the wall, I discovered that they had overcharged me by nearly $20. They measured the length of the boards as 65 feet, when they were only 49 feet long. Thankfully, after a brief talk with a manager, the customer service rep decided to trust my word and give me a full refund.
I bought some of the standard size composite baseboard and some pine quarter round. Those were the cheapest options, and together are just thick enough to hide the largest gaps between the flooring and the wall. (I thought the shoe molding looked a little better, but it was the same price and I'd have to buy more it it as I already had several 1 to 4 ft long scraps of quarter round laying around.) The boards came in 16ft length and I would have liked to have single pieces long enough for whole walls (14'5" and 12'7"), but I had them cut down to 12' instead because that is the longest I could fit in my vehicle.
I realized after returning home that I probably should have bought some more silicon and/or caulk while there, as Eli recommended sealing the edges of all the boards and the transition strip with it. I still have several partial tubes I brought home from Habitat, but I don't think they will be enough. I could probably take some more home on Saturday for free, but that would require postponing the baseboard installation. I need to return all the borrowed tools on Saturday morning, including the compound miter saw. I guess I could measure and cut the boards in advance but nail them later if I have to.
