I recommend you trying out "Horizontal build" approach. It's to walk you through the entire game loop but without functional features. So basically you make a sign or print the name of the functions that you're supposed to use during each parts of the game. Unless your game is a wave-based game like my past jam games, then I think it's fair to use this approach and try to finish the most you could.
Remember we can continued to polish the game even after the jam. So the most important part right now is to have "something" to submit in the jam.
I understood the rusty feeling you have. There was a year that I completely out of gamedev circle because I had to focused on university. Then there were many periods which I stopped gamedev for 3 months at the very least and 6 months at most in the past 5 years due to burnout which originated from bad management on myself.
But the most prominent part would be the expectation you have in yourself VS your real skills. Most of the time it could be you overestimated your body limits because you didn't understand the maintenance period for human enough, which is common and understandable. Then it's also the ignorant to the workflow. I used to struggle so hard on stuffs, but once I discovered that I had workflow issue, I just start learning from 0 and focus on the workflow itself instead of the qualities. Of course skills issue is the reality that we have to live with, since the industry set the standard too high. That's why I'm aiming to make my games with the quality of 2009 instead of trying to keep up. This way I won't have much floor to aim to, so the skills issue won't be long before it's completely disappeared.