1) Can I know my son's waiting list number in Sir Henry Floyd? How?
You need to ask the school because they maintain their own waiting list for Late Transfer applications.
2) Does the distance between my residence and school matter?
Yes, it does. Places for SHF are allocated in distance order (after some other categories), with catchment children having priority.
3) I live just outside the school's catchment area. I am ready to change my residence if it fetches a place for my son.
Although the school's Admissions Policy doesn't specify the timetable for any change of address, I suspect that they will continue to use the address where you were resident at the time of testing, whatever you do.
Can I put this point in appeal form? Any improvement of chances?
It won't help an appeal at all, and a panel would probably take a very dim view of you stating that you are happy to jump the queue by moving house.
If I can't put it in the appeal form, what else can I do?'
Apply for an appeal, put forward the best case you can and hope that it is successful.