Help with abs workout and overall muscle growth?

Hey guys, i started a workout routine about a month and a half ago. I'm doing a 3 day split, day 1 arms, chest and abs, day 2 back, shoulders and abs, day 3 legs. This is something someone recommended to me. I have about 13 % body fat, and although i've been trying to gain muscle, i'm also trying to lose a little bit more fat to lower this % and get the abs that i want. I've been very careful with what i've been eating and i have noticed that i have gotten leaner, and some muscle growth but my overall weight (in terms of muscle) has not grown as much as i'd like it. Basically my question is should i be eating more? I would like to gain some weight, but NOT fat!

- How can i eat more and not store more fat?

- Do muscles need more calories to grow, or is it just protein? (Which i've been eating a lot of, between protein shakes, bars, and protein rich foods)

- Another thing, i'm doing SOME cardio, but i'm afraid of doing more because i don't want to lose anymore weight, would my abs be able to burn the little bit of fat left on them (lower abs) by strength training alone?

Thanks guys, sorry for the long question but i'm just not sure what to do.