Hi honey...
I can relate to the sleeping problems... my son was pretty irregular.. then when he was about 3 months old I found an article, followed it to the letter, and within the week he was sleeping with minimal interruption from 8:30 pm to 6:30 am. Here's what you do:
1. Pick a time for your baby to go to bed, no matter WHAT. We chose 8:30 so we could have some alone time before we went to bed. In your case, you might want to make baby's bedtime an hour earlier than your toddler's bedtime, that way the toddler won't be kept up by the baby.
2. About 15-20 minutes before bedtime, give your baby a nice soothing bath, dress him in some comfy jammies, give him a little bit of milk or water (if milk, clean out his mouth afterwards). Just get him comfortable, and used to the idea of a winding down routine. Talk to him, coo and make him feel calm, safe and secure. He'll feel it, even if the first few days he still seems wound up. Also, make sure he's burped.
3. Turn out the lights in his room except for a night light... pull up a glider, rocker, or comfy chair next to his crib and put him in there. He'll kick and scream and yell, but you just sit in your chair and take a little nap. He'll calm down eventually and go to sleep, even if you have to tune him out until he does. (Your being there will make him feel safe, which will eventually calm him enough to get over being in his crib). If he cries for, say, over 30 minutes, it's okay to reach in and stroke his hair, belly, back, whatever works. He'll eventually stop crying and just pass out. Whatever you do, DO NOT PICK HIM UP. If you do, it'll turn into a game of control.
4. Keep doing this every night. You'll notice that he'll start fussing a lot less when he's put in his crib. After a couple of days to a week (maybe more, depending on your little guy) you should be able to move your chair away from the side of the crib to the center of the room. Then, after that, you move the chair to the doorway. This lets him have a smoother transition. Eventually he'll be ready to go straight into his crib with no fuss, since he'll be programmed for sleeping at 8:30. My little guy was already rubbing his eyes by 8:15!
I REALLY hope this helps you. It can take a lot of patience, since you;ll basically have to sit there and just tough it out while he yells, but if you stick with it you'll have a regularly sleeping kid in about a month or less. I felt this system was a lot kinder than the one where youjust plunk them down, leave the room and let them cry it out.
As for your toddler not letting you sleep.. I think you're right, the poor tyke just wants her mommy to herself. I noticed you said you try to occupy her with something else... have you tried making her mommy's helper? It worked with my baby's cousin... she was starting to get very jealous, and then I decided to make her Auntie's Special Helper and she would hand me his diaper, or his bottle of shampoo, or the box of cereal, nd help keep the baby entertained. She got lots and lots of praise for her efforts, and she felt like she was a part of the whole thing instead of feeling like she had to compete with my baby. And since she was sharing the work, by the time I was ready for my nap, she was ready to take one with me, and that was special Auntie time too.
Keep me updated, and good luck! :-)