Wow! What a turn around! Over the last two days I have been keeping lo up longer and his naps have transformed! Today his morning nap was 2 hours and he's currently asleep for his second nap and that's coming up on 2 hours too! He's also slept through the night for two nights in a row! It's been tough to keep him going for the two hours of awake time but it's totally worth it for have him napping so well!
I think the confusing aspect is that the wake time conflicts with his tiredness cues. After about 1.5 hours he displays strong signs of tiredness, rubbing his eyes, yawning, fussing - he appears so ready for sleep but although tired, he just wasn't tired enough.
Thank you very much for your advice, I really appreciate it!