Oh, boy where should I start...
Search this forum about DCA, you won't find a lot of positive comments.
If you chose carefully, an FBO can provide everything you need at about 1/3 the cost of most of the glossy-brochure academies. ATP seems to have a reasonable program, but my experience with them is limited.
Realistically, you will need a COMM SE & ME, IR, CFI, CFII, and MEI (sounds like you have some ratings already).
You will NOT need training on airline operations, turbine aircraft systems, or RJ sim training or a type rating. Somebody will try to sell you this stuff because it will make them a lot of money (your money actually).
If you feel uncomfortable with turbine aircraft systems, read the Turbine Pilot's Flight Manual or maybe take a class, but wait until you are approaching regional airline hiring minimums.
Also, be aware that many folks are trying to feed/support their families on regional airline pay, and the last thing they want to hear is a newbie say is "I don't need money, I just like to fly"...every person who arrives in the industry with that attitude lowers the compensation bar for the rest of us. I'm more or less in the same boat as you, but if I'm going to go to work, I might as well get paid as much as I can! Your financial situation will allow you to comfortably pursue your training, but PLEASE do not acquire a job simply because you are willing to work for less money than anyone else. Stay away from mesa, freedom, and gojets, etc. The pilots who jump on the real bottom-feeder opportunities are not highly regarded by their peers in the industry.
Good Luck