must...resist...urge... to ....buy.....pretty....fish....
Your system really isn't ready for a dwarf angel, especially flames, they can be "not easy" let's say.
honestly you should NEVER add new livestock while you are still getting ammonia readings because that is certain indicator that your system is not able to manage the bio-load you already had and now adding more critters will compound the problem.
Trust me, I know, If I had my way I would have another 4-5 tanks going, and I have four running already...LOL
but you must resist the urge to buy more stuff for at least another month.