hmm after messing around with my phone more... i found a temporary solution for the mp4 video problem (Y) probably the only solution you may be able to find on the net now so yayyy i'm very proud of myself
for some strange reasons, if you use RealPlayer to download videos from the net (once installed, hover cursor over vid screen and a tab appears 'Download This Video'), like from youtube or other players (though some, like MySpace vids may not work), and then you use the RealPlayer's Converter to convert it with the following custom settings:
Video
Format - Windows Media (.wmv)
Quality - 512 kbps
Resolution - 480 X 320
Audio
Format - AAC
Quality - 256 kbps stereo
(no variable bit rate, though I haven't really tried this)
If you use those settings to directly convert the downloaded video, amazingly, there is reduced lag in the audio/video sync, or in fact, NO LAG! Wahahahaha.
Been testing out anime episodes (in particular if you wanna try, go onepieceofbleach and download FMA episodes) and some short music videos, and they seem to work perfectly fine. well the quality downloaded from youtube is not the best i guess, but HEY. it's better than the sickening audio/video sync issue.
hope this helps! and oh for the contacts issue i've just resorted to diligently sorting out my google contacts T.T but it pays off well cos all the info is just in one contact card, and that's pretty damn awesome when you show off to your iPhone addicted friends