You could say: my 'old self' - it isn't anything to do with age, just someone who you were before you changed for whatever reason; age, ability, attitude, etc.

Neither. Just say: Could we try this again later? ;)

I would say that 'stutter' describes when the flow of speech is interrupted, usually associated with speech problems, as with 'stammer', if somebody has a stammer, they may repeat a word or hesitate with words during sentences. Whilst 'stumble' is generally associated with something physical, like a fall - somebody might accidentally stumble/ or lose their balance, or you could 'stumble upon' something, which would mean to find information, which isn't falling over at all!

'Settle down' is a phrasal verb, usually used when people have children, get married and settle down. You could use 'settle on' a price, which would mean to mutually agree on a price, e.g. we settled on a price I was happy with, but 'settle up' would be used to pay something that you owe to someone, e.g. you might settle up with a friend that paid for the dinner last night because you forgot your visa. I think your best bet would be to 'settle on a price' Hope that helps!

Answer below :)