For the save-progress question: since this is a fan game, it likely won't have native save states. Your best bet is to run it in an emulator or frontend that supports save states (RetroArch and similar tools let you snapshot progress with a hotkey), or use a generic tool like Cheat Engine's built-in "Save/Load" isn't for game state, but a save-state utility such as SaveState or the game's own quicksave if one exists
. That way you can snapshot right before the hard jump and reload instantly instead of backtracking from the save point every time.
For the invincible-boss issue with your CE table: that usually means your health/invincibility address is a shared value that also covers bosses. Try pointer-scanning to find a player-only structure, or freeze the value only during normal play and toggle it off just before boss rooms. Might be worth posting your table so someone can narrow the address down.