A Wilson Steam strung with a multi would be a rocket launcher for me. I agree that adding more topspin is probably the answer. You may not be able to do this immediately. In the meantime you probably want to do something that will let you swing out on the ball with more confidence.
Can your arm handle a poly? That would probably tame the racquet a bit. If you need a softer string, Head RIP Control is a lower powered multi. Very comfortable strung in the low 60's. Adding lead will make the racquet more powerful if you maintain the same swing speed.