Congratulations on your first fully finished-and-out-there game! :) Balancing is definitely tricky.. I think the best way to approach it is to just have a few people of various gaming skill levels play your game as you watch what they do. That’s not only great for finding a good difficulty balance, but it will also help you find other things you might not have noticed. Good luck on your game making journey! :D
Most of my playtests were also done online. I built a Windows desktop version of the game and sent it to friends, and they streamed themselves playing it over discord.
I also think you can publish the game to twitch in such a way that only certain accounts can access the game - that way you can have it be online without actually submitting it for the jam.
But I also saw a lot of people submitted their games early, and kept updating them before the deadline.