@Muchis
ah i had the same problems on my character. i was playing gdwitt's submod and you weren't so i guess this is a problem common to main bw
it's good you know when it happened. i went for a long time before i realized i wasn't in my own party anymore so i couldn't trace it back and just went with it. i wonder if the 2 problems are linked, getting knocked out to permanent low health and being removed from the party screen -- maybe the computer thinks you're dead.
and they must be related also because what are the chances you got the same 2 bugs i had
unfortunately i don't have much helpful information
the main character disappearing, i haven't fixed. you'll notice your party skill boosts also disappeared as if you aren't a member of the party, so you don't give the bonuses like +2 engineering. whoever is in the #1 position stays there until death, so it would be best to have a group of soldiers there who won't all be dying soon instead of a companion so that you can still talk to the companion. i had ceawlin there for a long time and could not change his gear. i think i ended up moving him out of my party with the savegame editor so the people below him in #2 slot (my archers, since i had many and they were a permanent staple of my army) could take up the 1st slot
for the health not regenerating, i tried all kinds of things. the submod has a horn that will heal you and i used it to boost my health to 100% in different places (battle, walking around town, in a siege) and hp would still go back down at the next loading area.
for that problem i got my health to come back by using m&b's savegame editor again. i uh... it's been some time what did i do... i tinkered with my main char, he's somewhere in there and i think i put his health to 100 in my last save. that fixed it for awhile. but sometimes when i got knocked out my health would permanently go down again and i had to use the editor again. so doing that would keep the glitch at bay for awhile at least. it had a greater chance of coming back if you got knocked out in battle, seemed like a random chance. but iirc it happened fewer and fewer like a wound that was healing and it stopped eventually
sorry for being almost completely useless at solving the problem, that's the best i could come up with at the time when i was playing