S.H.
Honestly, I think you're looking at a mix of different issues:
he has an established sleep/wake pattern. You need to work on changing this. At 9 months, he should be able to sleep thru the night - or at least 6 hours straight. His little body needs continuous sleep to "rest". Take a look at his naptimes during the day. At 9 months, he should be down to 2-3 naps. A morning nap, an afternoon nap, & perhaps a little catnap around dinnertime (not all children take this last one if bedtime is early). Take a look at his bedtime, too. You may want to contact your local hospital's sleep clinic for ideas on how to work this out.
My vote is to feed him more food & make sure he's using a sippy cup, too. Give him cereal before bedtime....it really does make a difference.
& now for the one thing which really jumps out at me: Your line "why doesn't he sleep for longer when we rock & sleep with him in the recliner". For me, that's your entire problem & issue in a nutshell. He is not trained to sleep independently IN his bed. He is now 9 months old & hasn't been taught to self-soothe. I realize that the CIO method is offensive to many & does not work for all babies.....BUT I truly, deep down in my heart, believe that children sleep more peacefully when not held by parents.
**in all fairness, this is MY opinion. Recently on this forum, many mamas feel they have the right to bash others' opinions. I truly, truly wish we could all have the freedom to express our own honest opinions .... without losing sight of the ultimate goal on this forum: to help others.
So, in a sense, this is a request/plea for each of us to focus on the end goal - to help this Mom! CIO, co-sleeping....are both "hot" topics on this forum. Let's be nice!