The problem with adding the STAR/TRANS/APPROACH is a known bug, that requires a trick that I explain in a Topic I created how to get it to hold, and give you a TD. Here is the link:

Fix for missing T/D in CDU/FMS

It should work for RNAV approaches!

Edit... As for the 767 not honouring the ALT Constraints. I don't recall having that happen to me.