Potty training Jack:(

So... I DID NOT want to potty train Jack at 23 months but it looks like I am going to.  I am STILL having trouble with my 3½ year old.  The kid will not poopy on the potty! I am desperate right now because I really want him to be fully potty trained by the time this third baby comes along.  He pees on the potty fine and stays dry all day but for some reason poops his pants everyday.  I have tried everything. Rewards, gumball machine, ice cream party, stickers...everything! Then I tried putting him in just underwear and no pull ups but after two weeks straight of cleaning out poopy underwear and not getting anywhere with it, I put him in pull ups because it is easier to clean up. I was desperate and I joined a "group" on the internet so I could post a question about "poopy training"  and the first suggestion was make him clean it up himself.  Gross. I couldn't imaging having him clean himself up and the underwear.  It seems like it would just make a bigger mess too.  Then someone said to just stop trying to potty train Jeremiah and start with Jack and then maybe Jeremiah will just start pooping on the potty since Jack will be.  I thought, hmmm...didn't really want to start training him until he was almost three but then again the thought of only having the baby in diapers sounds really nice.  So, I decided last night why not try.  We started last night when I got home from work and so far Jack peed twice last night on the potty and two times today.  He stayed dry all morning but did have a wet diaper when he woke up from his nap.  Not bad though.  Still not getting my hopes up.  And Jeremiah was all about it because I told him that since he was big he had to teach Jack how to pee and poop on the potty.  He was thrilled.  But not thrilled enough because he pooped in his pants when Jack was sleeping. UGH! And it was 30 min after I made him sit on the potty for about 20 minutes to "try" to go poop. I am ready to just throw my hands up with him and say screw it.  It's not like he HAS to be trained to go to preschool or anything.