Not being able to set other users to groups higher than your own is a security measure. This practice is inherited from the old LDU/Seditio days when usergroups relied on 'levels' instead of 'rights'. With the new rights system where it's possible to be a member of multiple groups this feature needs to be revised. Normally it's not a problem as long as the maingroup is always the highest, but that's not always the case. I'll add a ticket for this, so it'll be fixed in the next release.
As for your other problems I will need some more details before I can give a sensible answer.