Alright, since you asked for feedback, here it is.
What you did (had basics before jam and made game during the jam) is totally acceptable. I recommend you point it out at the top of your game page. For now it's a wall of text, that jammers don't have time to read, where you bragging with PvE and PvP modes and types of weapons and so on, seems supsicious that you didn't make it for the jam. I had to ctrl+F for "jam" to find the info that you actually made the game (most of it) for jam and during the jam.
What makes game a game is not quite what you say. You had bean shaped enemies and now you have skeletons, but it's not that important actually. A game is the abiltiy for a player to enjoy your game, and there's not much of it. Think of an actual human being, not familiar with your game at all, with random skills at gaming, loading your game for the first time. They spawn on that island with npcs with no directions, what should a player do? For example, I went to instuctor who offered me to pass 13 drills. Am I supposed to pass all of them right now? If I do - is it fun? Sadly - no, it's not fun. Limiting player to 1 move, offering a player to kill 2 enemies with that move, then unlockng the next move - would already be more fun. Same for reaper with 200 enemies - it's straight up impossible to kill that many, and if it is - it's not fun to even play for that long.
What I recommend you doing is vastly limiting your scope and trying to polish it, until it feels like a small but finished game. A game that a random person with no context can launch and enjoy. With game design and level deisgn subtly, or explicitly, telling them what to do to explerience most fun. Game jams are actually best place to do that - you just need to focus on a smaller game, finish and polish it. You can (and should) bring your creativity to the jam, and develop you skills of keeping scope under control and finishing what you do.
Maybe you came to the wrong place. If you want feedback on such an ambitious project, jammers who are on a rating spree, 5 mins per game, won't help you. Start a devlog, gather community, do regular updates on your progress and get continuous feedback. But trust me, once you focus one one thing, you'll realize that making a kill on a skeleton with a sword feel great takes 5+ testers and a month+ of real time for trial and error and balancing. And once you done that, you can continue with other weapons and mechanics - or decide to limit/remove them at all! Small-scoped finished game is better than any unfinished one!
Now for game itself. I'm sure you can make fullscreen a default option, and native resolution to be default. Sensitivity belongs to "controls" section of menus. Graphics look great, you could go for that cartooney outlined style if you wanted. Moveset is probably huge (I didn't spend time to discover everything) and is somewhat telegraphed, both from player and enemies, but it must be much better telegraphed. For now swing is slowed at the end, then suddenly there's a hit. A hit must be telegraphed most, so it probably must start with a slowly accelerating swing itself. Every combo move must have a bright/loud cue when you execute it, the moment you execute it. If you want to go for 200 enemies night - it's possible, but you must kill 3 skeletons with 1 swing, not 1 sleketon in 3 hits.
Overall, the project seems super-duper-extra promising. I can't rate it high in this jam, but I wish you best of luck in whatever you do in the future. Whether you decide to make a proper small jam game, or continue a big ambitious project. Anyways congrats on a cool submission!