I'm so glad you're enjoying the game! :DDD
You can download any new update and copy your save files over, and everything should work just fine! You will be able to continue without staring over!
The most common way to get dollars is, yeah, finding them in the wild or finding items you can sell to a collector. Technically some monsters have a chance to drop sellable items, but they generally aren't super reliable for grinding for cash. Money can be pretty sparse sometimes.
Honestly, after some thought, money being as sparse as it is makes for an even better experience. I'm able to buy at least one thing whenever I encounter a shop but never everything, and that extra choice is more interesting than the usual RPG experience of having so much money shops are just places you're able to pick up everything you need and then some. Not having healing items in shops also makes them feel important to use and saving items feels like a necessary habit to have learned - unlike other RPGs where you can just buy more potions before going into a dungeon.
I've read other comments so I understand why you aren't charging for this game but I honestly believe that without the copyright issues it really is worth paying for. If you have a Ko-Fi or Paypal or Patreon or anything I genuinely want to pay money for the experience I'm having playing this game.
Thanks! I wanted it to feel like you were scavenging for supplies to survive, so you'd really think about using healing items!
I do have a kofi, here! https://ko-fi.com/unity#
Any donations are very much appreciated! :D Maybe someday I can make an updated rerelease with all-original music and updated content to put on Steam or something, but for now I'm not sure if that'll happen
