Hi sonumish! I'm not really sure about the first half being thicker and the second half more watery, but if your semen analysis have come back normal, I don't think it's anything to worry about. In general, it usually takes about 30 minutes or so for the semen to liquify, so it's normal for it to be a bit thicker when just released. As for the volume, I think between 2-4 ml is normal.
There's also a urology forum on here, in case you want to try posting your questions there, too:
http://www.medhelp.org/forums/show/52
Good luck to you!