If I was telling someone "you're most welcome, and accepted." should I've said most welcomed instead of welcome?
In American English (and British English so far as I know) the idiom is "You're welcome"
you're welcome idiom
used as a response after being thanked by someone
Saying "You're welcomed" sounds strange and only makes sense if you're describing the actual process of being welcomed to someone in the second person, for example in the sentence: "You are welcomed into the house by your host".
I should say, I've never heard anyone use the additional "and accepted" part of this phrase. In the US, at least, the phrase is just "You're [most/very] welcome".