That might not be so easy to repair properly. The threaded rod welded to the LNB feed arms ends looks like aluminum and the nuts were uncoated or zinc plated steel. (that's probably why they broke cause they were rusted solid to due dissimilar metal corrosion). Is it possible to weld steel to aluminum? If not then he'll have to get more aluminum threaded rod (maybe expensive or very hard to obtain ).
My recommendation would be to use stainless steel hardware to prevent further corrosion. He might get away with using what's left of the threaded rod without welding more to it but moving the nuts farther up might screw up his F/D setting.
You can't weld aluminum to steel. However, new aluminum threaded rods can be attached to the old arm using a TIG welder. TIG was designed for welding aluminum. I've fixed boats with 16 gauge aluminum hulls that had holes knocked in them running into a pier or rocks. I loaned a friend my Ranger aluminum hull boat to take to Canada and gave him explicit instructions that the ratchet could not be riding against the boat while driving down the road or it would wear a hole through the metal.
He never paid attention and when he brought the boat back, he had some jack leg try to fix it and it had a pin hole that he didn't get welded. I had to grind it all down and fix it right myself. I was hot under the collar. I loaned him the boat and let him use my cabin at Gin Lake in Canada for a week free of charge, and he screwed up my boat. It was a mess when it came back. I never let him use either again.