Do you have a case worker? Talk to them. Please be aware too that if your disabilities are significant enough to impair parenting ability that the child welfare system could step in if you have a baby.
There is welfare for the baby if you qualify, but unless the baby is also disabled there aren't any financial benefits for them. Survivors benefits are for kids who have a deceased parent who paid in from their income while they were alive.
Yes, its possible to get married, assuming neither of you have a guardian who would need to consent. Be aware that what social security allows for married disabled couples is far less than what you get as single people. Its better financially not to get married unless you have another source of income.
It is possible that there may be too many barriers here for you to be able to have housing, have enough money, have the support of those who provide services to you, and have a baby. Sometimes we don't always get to have what we dream about, and if that becomes true for you, I would encourage you to seek out a source of support - your family, friends, church, or others to help you cope.
Edit to respond to your additional details: So both of you receive RSDI - that stands for Retirement, Survivors, and Disability Insurance. It's confusing when you call it survivors benefits since there has been no death. But you are correct that it is the same source of money - it just applies to a variety of circumstances. In a future child's case if they are eligible, the basis of eligibility would be disability. Not retirement, not survivor. It's less confusing to just say they would get social security benefits.