Well as I said, you should not do anything that hurts your situation or damages your standing with kapla and sounds like relisting those videos on any account would, so that's an easy decision, no.
As for the rest, the biggest issue I see (and I've done it too) with communication is not being clear and direct which is what makes people uneasy. That's why sometimes the asshole at work is easier to get along with then the friendly guy who seems noncommittal most of the time. At least with the asshole you know where you stand and can work with that.
In your case, just my 2 cents, but I'd be direct, honest and fair and say look any video you help me with the split will be X for you and Y for me. And Y will always be bigger then X because I am the one with the relationship with kapla and I am the one they are sponsoring. Maybe if you agree to help him create a few video's of his own (mind you I have no clue how much time this takes) and he can monetize those then that's all you need to do, no money split etc. But if you are planning on using him more in future videos you need to come up with a fair split (or pay him for his time), that is the right thing to do.