Help with my first engine build (5.9 Magnum)

If I could find a valve seat cutting tool, do you think that could solve my valve seat issue? Along with fresh exhaust valves of course. Trying to avoid the machine shop if possible and do what I can on my own.

What happens if I keep lapping the valves until the pitting goes away? Would this produce other issues? I ask because I lapped one of my valves again and the pitting was less defined. It seems like I could lap them 4 - 5 times and have a usable surface (each time lapping the valve until I feel the lapping compound smoothing out, then I remove the valve and clean everything before adding compound again).