I would have said, in a loud voice, "YOU NEED TO BACK AWAY AND STOP TALKING ABOUT MY BREASTS" when he leaned in and got within inches of my face and started making lurid comments about my breasts.
If the family knows he does this activity then it's their job to manage him in public. They must know how incredibly rude he is.
In developmental disability fields we have whole sheets of goals, outcomes, implementation strategies for teaching people person space and how to socially interact with people in different ways. Such as hugging mom compared to hugging a cashier at Walmart compared to how they are allowed to greet people in the work place.
He was booted from your business due to being rude, suggestive, inappropriate, and unsupervised by his family where they must know he acts completely incorrect.
If a review of your business is put on any community pages in FB please make sure you boldly tell your side of the story such as this.
I was standing at my post waiting for customers to enter our place and a man walked up to me and acted in a flirtatious manner. But it quickly became very uncomfortable for me as he moved on to getting right up next to me and leaning in towards my face, making comments about my breasts, .....(add every detail here) to such a point that I contacted the manager on duty. I was very uncomfortable at this point. When the man came back again I pointed him out to the manager and he asked the man to leave due to his inappropriate actions toward me, the manager thought he was high or perhaps drunk since he was stumbling around. After this people came up and informed us this man was autistic. He was not being supervised by his family nor did they step in and tell him to step back from me nor did they try to teach him about personal space and things that are not acceptable in the community."
This will share your side of the story in a way that shows you had no idea he was handicapped nor did he have family that was overseeing his experience in the community setting. This is sad, so sad for him and who he represents when he's out in the community. I would feel the same as you but I would have loudly told him that my breasts are none of his concern and if he didn't go find a seat until it was time for him to be seated he would have to leave.
Then every single person in the waiting area would have known he was saying crude and rude things to you and watched him more closely for you and perhaps his family would have intervened sooner.