Can never know for sure, and it is a little tighter than my preference.

If I was in your shoes though I would risk it and feel pretty good about taking the 7:30am ferry from RT.

-7:30am ferry gets you to STT at 8:30am
(Let's say there is a 30 minute delay, so call it 9:00am)
-Then let's say 1.5 hours for Customs (usually is significantly faster than this but be safe)
-9:00am to 10:30am
-Then 15 minute taxi ride to airport
-That puts you to the airport at 10:45am, still an hour ahead of your flight which should allow you to make it