Newborn awake too much?

My baby is 3 and a half weeks old. He's a really chill baby, doesn't fuss too much and is generally pretty content (which is a huge blessing because we're having serious feeding issues). I just learned that he might not be sleeping enough though. He usually goes to bed in the evening around 8, will sleep for 4-5 hours, wake up for an hour to eat and sleep for another 3 hours. By around 4 or 5 am he is usually awake and will stay awake for about 2 hours. Then nap on and off throughout the day. It's pretty normal for him to stay awake for 2-3 hours twice a day. I wasn't concerned until I read an article about newborn sleep, saying babies shouldn't stay awake for more than 1.5 hours at a time. Now I'm so nervous!

I was thinking about it, and the second time he wakes up in the night he usually stays awake for about 20 minutes before I get up to feed him. I try, but I can't get my body to wake up in a timely manor because he doesn't cry, he just breathes heavily, so it doesn't really wake me. I'm wondering if he gets over tired/upset at this time, and that makes it harder for him to fall asleep.