I don't have the best track record with RPs I GM, either.
Let's hope for the best.
As for your request, the Dominion would have a hard time trusting a faction that doesn't at least tell their home planet. They need to be contact with the leadership and set up an embassy, afterall. Being in the Dominion is a privelige they grant, as they express. You can have territories you hide, though but if the Dominion gets wind of it that won't make them too happy. Otherwise the rest is acceptable.
Also keep in mind that the game is just a bunch of battles. Rest is done by intermission like narration. Nobody really going to attack yor homeworld unless you allow it (and that still requires the Dominion doing badly in war). Generally successful attacks on homeworlds would often mean the faction's gradual collapse. of corse there are ways to save but generally only do this if you want a chance to exit the game. Alternatively just do it for excitement. But yeah, generally it's up to you to allow attacks on yor faction's worlds. If you don't want that we can try finding somebody else.
So you shouldn't worry about this.