I am NO expert on "trapping", it is not something I do. But if it were me, I would put Macy's feeding station as close to the garage door as she will let you that she will still eat from it. And then each time you fill it, move it closer and closer to the door. Then it will not seem so strange to go near that door (open OR closed).
As far as fostering, yes, it is hard but it is also VERY rewarding. Only you can decide IF it is for you or not, but keep in mind what the outcome would be if no one bothered. I cry a little each time I take the babies to adoption days because it may be the last time I ever see them. But the joy they gave me is a wonderful feeling and knowing that if I were not there for them they may not even have their precious little lives.