I believe so. If you are an expert of persuasion with all 5 persuasion points, that should be the maximum you can get.
It depends on CH. With 18 CH, you can not do better than 7,000 gp. With 19 or 20, you can get 11,000 & Ambasador status.
Hmm... forget about Tarant, you should help Caladon, then a lot of people and bribe you for making the negotiations to benefit them, Or if Caladon doesn't join you can always trust Maxim will make his aircraft army to blow Tarant. ...but maybe you want to become Master and Willoughsby won't train you, although I made Caladon join with everything to their favour and Willoughsby still paid me, like 3000.