If I had to condense my advice into a couple tips, it would be to try to gain as much weight as possible as quickly as possible in the earlier rounds (up to ~20 or so) so you can get as many helpers as you can, then try to keep your weight low with antimatter cakes so you have a better chance at dodging bullets. If I were to recommend a character it would be either Sally or Bella as they have the tightest hitboxes and the best powerup cake-exclusive helpers. Good luck man!
Yeah 42 is the best I can do thanks for the help. It gets harder than dark souls after that.