...The main point of this is to get info on the next rod I should get. My current setup is a Bass Pro 8wt that was like $150 and frankly I just use it for bass.
Maybe I should just get a 6 weight because really I would only fish for Bass, Carp, Catfish, Trout both fresh and salt and redfish. Tarpon, Spanish, Jacks and others could wait until maybe I get more experience. ...
You answered your own question.
Something to consider: Since you have an 8wt and are looking at a lifetime of doing this, consider sticking to even numbered wt. for the intermediate future purchases. Make purchases according to your needs based on target fish.
In your case, that would logically point to the next purchase of a 6wt.
From there, purchases can be based on need, e.g. go to 4 wt for more finesse fishing or go to 10 wt and get into some of the big powerful fish out there.
Until you get into 10 wt class, IMO, you needn't worry much about reels. They are basically just line holders at 8wt and below and do not warrant large $ investments. ( of course there are exceptions for certain fish like Steelhead and King salmon for example)
Other stuff:
1) Mullet, yes I've successfully thrown some bread flies at them...and milkfish are over rated IMO.
2) The main reason for NOT using a 7wt on large Tarpon (and other precious game fish) is to protect the great fish. 180 to 200 pound Tarpon are precious resources that should not be wasted on 7wt rods. Releasing a Tarpon after an exhausting fight on undersized equipment is almost certain death for a great, great fish. Egos should be set aside and the well being of the fish considered paramount. Don't even consider using 7wt on large Tarpon.
3) Lines are generally worth the money. A high quality Rio line for example, if taken care of, will last indefinitely in salt or fresh. They are well worth the investment.
Just my 2cents.