Exterior Door is Sticking - What is causing it and how do I fix it?

Remove the interior trim. from the side where you have the bow in the jamb. There may be shims there. if so take one out and drive a 2 1/2 in. screw in the jamb this should pull the jamb back to plumb. as for the outside replace the board. but before you put the new one in make sure you silicone under the sill well.