No, neither nukes or razings have a direct influence in either RTT or capitulation besides the changes in war success ( 10 war success points per detonated nuke , BTW ).
In your situation ... well, I'll assume that Victoria is weaker than Wash and Wash weaker than Boudica . In that situation it is impossible that either Boudica or Victoria vassal peacefully to Wash, that is a good thing, so the only risk is from them to capitulate to him. As long as Boudica is stronger than him , that should not happen, but Victoria, being weaker, might have a risk of capitulating to Wash if Wash has 40+ war sucess points on her and she becomes free ( might be dificult to have that war sucess if the war was really mainly naval ). Same to Boudica if she becomes sustantially weaker than Wash and if Victoria breaks free...
I've had a lot of games where I'm devastating an opponent after getting ahead in a long war, and they suddenly capitulate to a third-party I'd only brought in as a bribed ally a few turns earlier and who didn't seem to be getting much of their territory. A little different scenario than what I've been describing. But is that just my perception? Did that third party have to have achieved some major success points that I'm just overlooking for this to happen? Also, does the overall history of the war shape the success evaluation, so that if I took heavy losses early, but now have the initiative, I may not be viewed as all that successful?
Guess in the Victoria/Wash scenario above, I may want to bribe Wash to make peace with her before she can Capitulate to him. Since they hate each other, that should also proclude her Vassaling to him before I can get her to bow to me.