I'm not sure about all the concern w/ the clowns, and gobies, and sixlines.
I don't think they will have any problem getting along.
I have had 2 clowns, 1 firefish (purple), 1 sixline, 1 royal gramma without any problem.
Now I have 2clowns, 1 RG, purple FF, and a midas blenny, again w/ no problem. I did a lot of research and posted my stocklist as you did, and got the Go-ahead from ppl on this forum.
IDK if you can mix the dottyback, blackcap, adn pseduochrmois. I think it may not be good, idk though.
Also, don't think you are obligated to get one of those fish, there are plenty of other LFS's