it seems odd that you trust him totally, but at the same time don't trust him at all. I am really puzzled by your line "I think eventually we will look at marriage but id like to know how this could work as he has no assets or savings"
are you saying marriage can only work if you both have assets and savings?
If you are this concerned about getting ripped off, it would probably be wisest to see a solictor. You seem to imply that you ultimately want to achieve leaving everything you own when you die to you your children, but what if you do marry and have 20, 25, 30 happy years together? If you ere to die first, would you not want to leave hom something? Somewhere to live?