I think there are a lot of variables here with the immigration to the US. I would think you may need to move and get a job here first and then bring him over so he can continue to get treated and covered in Canada. Of coarse that may mean being apart for a little while. I would not recommend moving him here without being able to go onto your work insurance, unless you have plenty of extra money in case he gets sick. You can't expect to move him here and immediately get 100% or even any aide. They must have waiting periods in this case.
As far as how much it costs to cover cf costs per year, that really depends on his health. Minimum it would be the cost of his meds plus say 3 or 4 doctor checkups. However, if he needs IV's once or more a year then it could be a lot. I would say a 2 week tune-up in a hospital here could average 50,000+ depending on the city/hospital. Home IV's would be less.