A) I have never seen the hit taken at the “end” of combat, it’s usually the first hit in the game. But that’s just me.
B) I agree your house rules are a bit on the lengthy/confusing side. Just my opinion here, but I think all house rules need to be a one step process that is very easy to remember and does not lend itself to needing to be referred back too by those using them for the first or second time.
Back on point:
I like two different rules for BBs that are damaged:
1) Damaged BBs stay damaged until they return to a home port (not just an allied IC, but one that the nation owning the battleship owns.)
or
2) Roll a D6 and that’s the IPC cost that has to be paid IMMEDIATELY to repair all damaged battleships. If insufficient funds are available to repair the ship, the ship is sunk. Since you collect income at the end of your turn, this should not be a problem. If you are damaged while attacking, you may use the money you collect at the end of your turn to repair the ship.
ie: America attacks with 1 battleship and damages it. They roll a die and get a 4. Since they spent all their money in the buy new units phase, they elect to pay for the repairs out of their end of round income. So instead of collecting 48 IPC, they collect 44 IPC.
Later, Japan attacks and again damages the Battleship, since America has not gone yet, they must immediately pay the 3 IPC the Japanese player rolled to repair the ship.
Note: You may only elect to sink the ship if you do not have the money needed to repair it. Sailors are not suicidal, they will not jump into the water and swim across the ocean just because you feel inconvenienced. hehe.
example 2:
England attacks the Italian Battleship damaging it and rolling a 6 on the die. Italy only has 4 IPC left because they damaged their BB previously and had to pay to repair it. Since they cannot afford to repair the ship again, it is lost and sunk with only the one hit.