noob cake question about xbox live

[BTNHfan99]

I've been playing on my xbox360 with friends since it was purchased. I've always used "JAY" as my default sign on name.

Now I just started playing on xbox live. I had halo 3 collecting dust for about half a year after it was purchased. it wasnt until 2 weeks ago that i tried out xbox live. so i signed up and created an xbox live account. so I did and the account name is BTNHfan

 

well I didnt think about it when i purchased gta iv but ever since i started playing (since the default sign on name is JAY) ive been using my "JAY" account. (the non xbox live account).

well yesterday i finaly tried out gta iv multi player, i tried to use it while i was on JAY but it said i had to log onto an xbox live account. So i logged onto BTNHfan** and i was able to play on live.

well JAY (the non xbox live account) is where my progress is saved. BTNHfan** on the other hand has no progress.

 

my questions are;

1)Does unlocking any achievements or making progress in the solo feature have any effect on the multiplayer feature? ie, clothes, maps, etc.

because i saw a few people in LIVE dressed as a cop and sh*t and i wondered if he got that outfit by playing on live or solo.

2)if so, is there any way I can transfer my game data onto my LIVE account (BTNHfan**) because I cant go on live with my JAY account.

3)am I able to make JAY an xbox live account?