You guys all need to do some reading on the topic: "Adverse Possession" - It will be enlightening.
AP has been mentioned at least twice. I'm not familiar with rules in other Midwestern states, but
in Michigan there is absolutely no such thing. I bought my property just after a neighbor had surveyed and sued PO for adverse possession, or at least clarify a 30' strip of adjoining property. Judgement of the court was that a house built in the '40s was 10' onto my property, and that any and all mods or replacements (roof, windows) would be done
only with the approval of the PO or later myself. 30' of their lot, and a half acre asparagus patch were also actually mine vs his. In our state, surveys are as solid as Oosik's basaltic bedrock.
Our problem never really existed once we met. A roughly equal amount of my 'presumed property' (and the West 650' of pond shore) was actually his. Within minutes of meeting we'd walked, talked, and agreed to a reasonable redo of lines that had been mistakenly thought 'true'. We had the lines re-surveyed to our hand-placed markers. (He declined my offer to pay half of the new survey) Our legal boundaries now match the tree lines long
thought to be accurate, but far from it. ~5/8 acre in total was 'traded'.
btw, I don't consider the OP to be a 'bad neighbor' by any means. For a neighbor to buy, then commercialize in absentia vs occupy doesn't fit my idea of being 'neighborly', and the container bit tips some balance with me. I think the OP is holding up very well to the scrutiny of us dingbats weirdos, and other oddballs that always think our advice is the most sound. Being the oddest, weirdest, dingbat following this I ought to know. I applaud the steps taken so far. No touch offender's stuff before zoning/legality of use is checked and lawyer is contacted.