Since you have a very low cycle count battery, I understand that you’d want to preserve it. However, due to your trackpad issues, I’d recommend a full upper case assembly anyways as removing the battery is a very tedious and unpleasant job and doesn’t require more steps. But, since you'd plan on replacing the battery anyways, I’d just do a trackpad replacement. You can find used ones on eBay for around $30 depending on where you are and you just need a plastic syringe and a bottle of acetone. Use a plastic card that you don’t need like an old gift card and try to open up some space. Just add a few drops, not a lot as you might risk damaging the cells. You can always add more so be very careful. Patience is very important for this job. But it can be done and it’s not very expensive to do it yourself.
70% alcohol is fine. I’ve used it for building/rebuilding many desktops and my CPU’s have been really cool. I also use nail polish remover wipes because they’re lint-free and clean really well Here’s a similar one to the one I have