Hi Howard
In my limited experience with angels, I've learned that some of the "fancier" types aren't hardy at all (in fact no angels are truly hardy, but the fancy ones are even worse) - steer clear of Kois, etc if you want slightly sturdier angels. Apparently silver angels are slightly hardier than most.
You can't sex angels without watching them breed, so if you want a pair you're better off buying 3 or 4 babies and selling the extras when they pair off (although I wouldn't recommend 4 babies from the same batch as that'll be inbreeding and angels are inbred enough), or buying a breeding pair. I wouldn't have more than 2 adult angels in with what you already have.
I would recommend having plenty of cash ready for imminent treatment, as stress seems to bring on quite severe and costly illness in angels, so tank moves etc are a risk. You'll probably be fine, but it's best to be ready (we weren't and my God it hit us hard!).
As for the tetras, I'm not really sure on that one as we don't have any smaller tetras any more (no they didn't get eaten *lol*), but I've seen lots of people keep angels with small tetras with no problems, and have also read on here about angels eating neon sized tetras. The Glowlights are the smallest aren't they? Mabe someone else can advise you on that side of things.
Best of luck!
Kathy