Son, if I even see a pic of you holding that damned thing without safety glasses on I will find your house and talk to your dad. Dude, honestly I am concerned for your safety, scared even. I work with a guy with a glass eye. Its fun to tap him on the back of the shoulder on his blind side and pick on him but seriously, you could loose both eyes. Ok, dad moment over on to the cool stuff.
That is neat. Squirrely boy has a point with the string loop wearing out from the screw rubbing it. Better to drill a hole and glue in a wooden dowel. 45# is good for a fun time with that. I think you can save the bow on that thing by removing the screws and filling the holes with wood glue mixed with saw dust.
Take that bow ( prod ) off and carve into the stock a notch wide as the bow for it to sit into. Then lay over the back of the prod a block of wood that is maybe 9 inches long. This will be what holds the prod in place and cover the holes to keep the prod from blowing up because of the screw holes. Using string, wrap the 9 inch long board to the stock of the cross bow. You may need to provide a spot on the stock to wrap the string too, drill a hole through behind the prod and glue in a thick dowel. The dowel needs to go into the stock left to right, same as the bow ( left to right ) and stick out either side an inch. Tie the 9 inch board to the dowel to hold the prod in place. This keeps it in place without screws and helps back it where the screws were. Your tiller looks pretty good.