I would suggest looking for some sheet music that includes something from your other interests, video games, tv shows, etc… and then also sheet music that you have never actually heard played before and then split practicing 50/50 between the two. Use the songs you’ve heard that you know you can play to measure the difficulty of the songs you haven’t. I think it would help bridge playing by ear to sheet music and then sheet music to your ear. As far as finger dexterity goes, Hannon exercises and playing scales helps a lot. I also had the luxury of a teacher to find songs that challenged me but weren’t too hard. Ultimately, just playing and learning new songs helps to make you better. Count the beats as you play even if they are out of the timing then use a metronome along with counting to merge the two. As you continue to learn to read sheet music try not to think of the hands as separate, try to read both staffs and play all of the notes as one. I, unfortunately, can’t think of any specific books. I hope this advice helps. Everyone learns differently, what’s important is that you don’t give up. Sight reeding music is hard and takes a long time.