Yeah those screws don't need to be all the way tight either. Since you said you stripped them out you may need to replace the screws or get a new FD.

There are lots of nice manuals online on how to adjust the FD, but basically you want to shift to the big cog in back, small ring in front, loosen the cable with the barrel adjusters until the cable is loose. Then set the low limit screw (the left one on the 105 I believe). You want the derailleur cage to just be almost touching the chain on the left side. Now that that's done shift to the small cog on the back and pull the wire tight with your hand. The FD should move over and push the chain up onto the big ring. You then set the right screw. You want the derailleur cage to almost touch on the right this time.

After this is done take up the slack with the barrel adjuster until the cable is taut.