what i would say is to stop the jumperoo thing first. that isnt nearly as important a connection as you are! trust me, babies (even 18 month old ones) need their mamas! one thing that might help is trying to put his bed in your room. that way, it isnt far to go, he might wake up sometimes, see that you are there, and go back to sleep on his own. my son did that a lot. he stopped night nursing on his own around 15-17 months, but then he also self weaned altogether with no provocation from me at 19-20 months.
dont ask, dont refuse. it sounds like the family bed is more than ok with you. if your husband wants his bed back, weaning to get pregnant isnt a great idea, that just brings another baby into bed, right? ALSO: it IS possible to get pregnant, and go through the entire pregnancy while still nursing. i have heard it helps with sibling rivalry, if the older child knows that nursing wont be taken away just because of the baby. your other ones sound fine, this one is just different. im surprised you got through 4 kids without running across one that has higher needs than the others! LOL my son was a high need baby from day one, and hes the only one we've got (he just turned 3).
one thing i would recommend, if you havent already, go to www.llli.org. contact a local or nearby la leche league group. you will LOVE IT!! :) i had to drive an hour for mind, but it was SO WORTH IT! they will have awesome, reliable information, as well as real mom information there too! they usually meet only once a month, so its not a huge time commitment. :) its awesome.
but basically, just have patience. this baby is just trying to tell you that he needs you. theres nothing wrong with him, or you, just keep doing what you are doign. you dont have to make him cry, you dont have to make him sleep alone. my son didnt until he was a bit over 2 years old, we only moved him to his own room just before he turned 3. the best thing is that he trusts us completely to come get him if he has a need at night, whether hes just scared or needs a drink. so much peace! he also goes to bed really well, no struggles or fights (until recently, hes teething some molars, and finally having some kinds of resisting mom and dad thing going on! LOL)
but anyway, you wont regret taking the time. ;)