I've done a few of these conversions although most often to make a single speed rather than a 1x. I usually move the chainring to the outer position and get a new bottom bracket to center the chainline so the chainring more or less aligns with the middle cog (usually a 68x107 bottom bracket). I have never bought new bolts but just chopped the old ones down with an angle grinder but I can see that getting new ones for $10 is probably easier. I've also never had a problem with chains dropping off but it maybe because I have always used older cranksets which did not have ramps or profiling to aid shifting. These ramps and cut-teeth, (used on most bikes from the bikes 1990's +). are specifically designed so a slight nudge with the derailleur and the chain will transfer easily to the the next gear but absent a front derailleur will facilitate the chain dropping off.