Okay. This is what i would do if it were my tank: I would change 50% every Friday. I try to keep my Nitrates 20 ppm or less. Plants will NOT absorb all Nitrates and that is where the partial Water Changes (PWCs) come in.
Keep doing what you're doing! Watch those Nitrates! Changing water is the cheapest way for healthy long-lived fish (and plants). I love to hear it when a newbie changes water!
if you can, get some more plants. they won't completely fix the problem but they'll help. there are also water treatments to help detoxify the nitrates in the water. i believe the one i've used is Prime from Seachem. Detoxifies Nitrates, Nitrites, and Ammonia. It's definitely helped me when I had high nitrate levels that I couldn't get under control. Good luck!