1.I go for a rescue attempt with King David with throne of David in play. I get inish from throne and band in asaph a few other heroes and ET last then use his ability…. Can I use my musicians chambers and play an enhancement from there.
You may, because ET's ability says that "Holder may play the next enhancement card". That means that you, as the holder, may play any card you can legally play, including those from Chamber since you have David and other musicians in battle.
2.If I have two heroes in battle can I use the purple brigade enhancement Ezeikiel’s stick to add in a third one (it’s a long shot…)
I'm fairly certain that this is just a regular old band ability, but you have a point about the wording. I think that we need clarification if this (and other similarly-worded) cards do not allow banding if there are multiple heroes in battle.
3.Is there any way to protect your fort from your own Samuel
Are you asking if you can protect from Samuel's negation of Play, in regards to TToD? Assuming that's the case based on the rest of the questions.
No, you cannot. Protect cannot stop interruption or negation, so even if a card could protect TToD from Samuel, it still would be negated.
4.If I go for a rescue attempt with Chenaniah banded to King Solomen, I have throne of David out so I play Royal Parade. Can the Evil character blocking me play a negate enhancement first off since my chenaniah is protecting my musicians from the first enhancement.
First, Chenaniah only protects musicians, not enhancements played on them. And as in #3, protection does not stop interruption or negation. So yes, they can negate Royal Parade.