On water flow would 3000 from powerheads and 500 possibly more from return pump be enough?
the only way to know if it's "enough" is to try it and see. You can strip the flesh of an acropora clean off with less than 300gph, likewise, you can still have low-flow issues with 50000000 gph. There are so many variables at play, it's impossible to give a concrete number.
Every tank is different, every coral is different. If you're looking for a checklist on how to raise a fantastic looking reef, you're not going to find it.
Instead of asking questions on every aspect, purchase some books and read as much as you can. Having a broad knowledge pool of reef related subjects makes the mistakes and problems easier to prevent and/or fix, and you WILL make mistakes, waste money, and kill some things. It's unavoidable.
If you don't have the patience, diligence, perseverence and wallet for trial and error, you won't do well in this hobby.