Your doujin is really great! *-* It's so nice when they are sleeping together, awwww!
Hm...600dpi is better. I rather draw on a smaller page then (not A4, but also not A5, I made myself some kind of manga side template with borders for left and right sites and also with bleed, although that doesn't matter when you draw a web comic...^^° )
Ah, and like I said in the nezushi's baby thread -> feel free to post your doujin here like that as well. (Of course just if you want. ^^) I guess it's nicer when people can read it in one piece and without have to enlarge the pictures.