7 month old only napping twice

My son is nearing 7 months old, and has dropped his third nap a few days ago. I wouldn't have a problem with this, except it means he has a long period of awake time in the evening, which makes him very clingy and cranky. He always wakes up between 5-6:30 every morning no matter what time he goes to bed, and he can only stay awake for 2-2 1/2 before he needs his first nap, and then he usually gets sleepy for his second nap around 1 p.m. After that, he downright refuses to nap. His bedtime is anywhere between 6-8:30 depending on how tired he is and how willing he is to go to sleep. Bedtime used to take 30 minutes, and now it takes 1-2 hours because he's so crabby, and it doesn't help that he's cutting his third tooth. He just WON'T take a third nap, no matter how tired he is or how hard I try. Any advice would be great!!