you should really try to see if your LFS will take the angel, as it will get WAY too big for your tank and having it live in a 10 gallon for 90 days will almost certainly kill it.
I know your frustration, as I too lost many fish when I first started (blue tang, naso tang, longnose butterfly, heniochus) due to my tank being too small. I have since stepped back and done some research and found smaller fish that thrive in my 55 gallon. I am probably still overstocked, but everyone has been doing very well for the past 3 to 4 months (4 green chromis, maroon clown, mandarin, keyhole angel, eibli angel (they get along...I know they normally don't, but these guys are weird that way), yellowtail damsel, and foxface (thinking of taking him to LFS, he is going to get too big for this tank and my upgrade won't be coming as soon as had originally planned).
When researching, look at several sites in order to find a general opinion as to minimum tank size (not looking for one that states that your tank size is good enough). This will help you find fish that you really like as well as ones that will do well in your tank. I found that adding inverts (porcelain crabs, anemone crabs, emerald crabs, peppermint and cleaner shrimp) and coral (if that is your plan) helps to add to the character of the tank without adding too much to the bioload or creating too many problems with compatibility (again, you need to research before buying).
Hang in there, regroup, do some research, and enjoy.