What happens if I don’t have enough space for the remaining resources from the season pass?

I am a TH9 CoC player, and I got confused also the first time when I saw the overflowing Season Bank Loot. But the thing is that the EXTRA loot still stays. Like your Storage of Gold is 4,000,000 and you have 3,000,000. Your season bank is 5,000,000. So you then have 8,000,000 gold even if your storage is only half the cash. But when it becomes 7,999,999 gold, it's not becoming 8,000,000 again.

I suggest you make armies that are almost 100% made of dark elixir troops.

You can also upgrade your hero.

As well as upgrading your dark elixir storage.

Continue doing so until you have enough space for your dark elixir.

Good luck!