Some complicated stuff!

[Mackiiboy]

I'm afraid you will have to turn your custom story into a full conversion if you already have not done that, if you want to disable auto health regain. It's possible to modify the speed of regain in the game.cfg file, but, you will need a FC for that. Complex timers would probably work too to work around the problem, but takes some time to make.

I might figure out something better later, but I will be busy for some hours now. Maybe someone else can help you during the time.
Good luck!