I have seen some of the things you are seeing.
1. Make sure Key Maps are off, I cycle mine to make sure. then turn on repeater and enter the password. I watch the alt to counts " * " so it should be close to right.
2. I put in a Key that I have to hold to swap screens, otherwise I can click on an alts and then go on without changing masters.
3. not sure, Ask Lax
4. is the problem only on the first spellcast? Sometimes the alts are slow to pick up the target. I will use an assist key so they are sure to have the same target. Otherwise, your group is telling different toons to follow different masters. Might be in Jamba settings.