You're most certainly welcome. Just always remember, people can give you all the advice in the world. And the elite players have a tried and true way of doing things (thats where I started with my learning). But, as I said before, it's a matter of playstyle. Do what works best for the way you play.
As for training dummies, simcraft, etc.
They are very helpful. They take your character, its gear, stats, everything and give you an unbelievably good idea as to what you would do in a raid situation, if you were standing there pounding on a boss that never moves and has minimal mechanics.
Thats great, but, most raid fights aren't like that. So don't put too much stock in those tools.
Your number one tool you can use? Experience. Jump in and do the fights. I great tool that lots of people use are videos of the actual boss fights on Youtube. I recommend using those posted by Fatboss. Those to British guys are very good at teaching the fight, the language is a little colorful, but to me it's worth the watch.
Once you have your rotation down, know how to gear (and modify your gear), and get experience, you're next step will be achieving that moment that you realize, as ret, I am not a pure dps class. What I mean by that is that you should never compare yourself, as ret, to other pure dps classes. You need to figure out how to be a utility player. Once you do, raiding is super fun. Using your off heal spells, your cleanses, your divine protections on other raid members makes you one of the most useful classes in wow. Not only will you be pulling very respectable dps, but you'll also be a valuable asset in other areas of the raid as well.
It takes time and patience, but you'll get there. I have no doubt. You reached out for help, that was the first step, and you seem to be following through. Makes me a proud ret pally. Anytime you need advice, or have questions, feel free to contact me. Also my battletag is Nimaj#1912 Feel free to add me that way, since I'm on alot, you can get insta answers. I never mind helping out whenever I can.