How much expressed milk to give before bed?

Hi ladies, a while back some of you recommended giving our little guy a bottle of expressed milk before bed rather than nursing him to make sure his tummy is nice and full in the hopes of getting him to sleep better. Well we want to try it tonight. Dad will do the bedtime routine all on his own for the first time ever.

Our biggest bottle holds 5oz, is that enough for him? He's almost exclusively nursed so I don't know how much he drinks all day. However, he drains every bottle he gets, no matter how much is in it or how hungry he is (the last bottle he drained was 5oz and he didn't spit up after).

He's 19 weeks tomorrow / 4 months 10 days. He's a big boy, has typically been around the 75th percentile. We think he weighs a little over 17 and a half pounds now, but don't have an exact number.

Thank you!

UPDATE:

This did not work for us. For the past three nights LO has woken up 2.5 hours after going to bed and has been difficult to get back down. The night just gets worse from there. I'm out of ideas.