I think this 2nd son is pretty serious, at last regarding his job and his people. The first you think that he talk like a clown, but actually what he talking about is how to benefit his tribe the most, meanwhile try to caugh Almus off guard.
Well Almus isnt caugh off guard and I think because of that he respected him a bit, and because of how open minded he is, he can be the way to forward the alliance.
Can he be trusted? Well just look at the factor one (for his tribe loyalty) so as long as the alliance bring great benefit (to them), you can trust him, and well its one of Almus job too (as a king) to make his ally never betray him.