If you can prove to the courts that either you, your attorney, or a private investigator can not locate your spouse, then you can proceed with a divorce by publication. This process is tricky, so consult with a matrimonial attorney asap
I suggest that you file and serve an amended summons or verified complaint with the grounds of irretrievable breakdown of your marriage. This is much easier to prove, and takes less time. If your husband decides to fight the case, the Judge will make it difficult for him, filing under this ground has the same effect as cruelty.
It should go to you and your siblings, howeve, if he creates a will he can leave his share to whomever he chooses. If your uncle does not have a will, you will need to go to surrogates court to establish your rights after he passes.
I assume you are talking about social security benefits. As long as you were married for more than 10 years you would be entitled to collect under your ex husband's benefits if that amount would be higher than the amount you would be able to obtain on your own. If you are talking about his pension or retirement benefits, it depends on the language in your settlement agreement. If your divorce judgement or settlement agreement was silent on this issue, you would not be entitled to any of his...
if their is no visitation order and he rarely sees the child you would have no problem getting an order from the Court allowing relocation. I suggest that you write the father and tell him of your plans to move. If he has no objection, just mover
Your husband can petition the courts for a modification of his custody order in an attempt to get physical custody of the child. However, he would have to prove that there has been a drastic change in circumstance, or the child is in harm living with the mother.
Its best to consult with an attorney regarding this.