Rest assured, the combat system has three modes: normal, easy and disabled.
Normal: pretty self explanatory
Easy: all of the changes in easy mode aren't finalized yet as I'll likely continue to tweak things even after this update comes out but the main difference is that Lilly gets her canonical powers in combat instead of her strength being nerfed to "reasonable" levels for normal meaning she'll do crazy damage and be quite tanky.
Disabled: if combat is disabled you'll get a small text description of the fight, including the dialogue that would normally play during the fight (if there is any).
You won't have to worry about save altering. I plan on keeping the full gallery unlock option free upon current content completion. So each main mission is a "chapter", as long as you have completed the latest chapter (even with combat disabled) you will be able to unlock the full gallery, combat sex scenes included (combat failure events and the pixel sprite mid combat grapple animations).
The only payments that will ever go into this game will be to purchase it on Steam once I get it launched there (if they allow it), support on subscribestar (please ) to get access to the newest version a month before it goes public and a post 1.0 dlc that I have planned for a female playable character. The female MC was originally part of my base game ambitions but the work required for it along with the playable anthro characters is just a step too far for the single artist I have to work on everything so it got pushed back. Retexturing male MC scenes is fairly simple since we can just put fur/scales on the body and slightly change penis shape and it is ready to go, but the female MC requires making completely new scenes along with those scenes anthro variants so it's just too costly to do properly.