good midnight all. so several years ago I posted about a high idle issue and that I had checked everything I could and couldn't pin point it well fast forward to this year and I decided to drop the engine and rebuild it. I'm very sad and need some input. So back in 09 when I acquired my 914 from my dad it had set since 86 because a spark plug had broken off in it. I pulled the head and got to looking at th cylinder to make sure no particles were in the cylinder. when I reinstalled the head I did not se that the seal ring was not properly set and it was wedged when everything got tightened down. so I need advice on the following pictures.
1. due to the slight depression from the ring I am thinking I need to have the seat honed I shouldn't need to replace the head correct?
2. what would be the best way to clean these hard deposits on the exhaust valves?
3. all of the sleeves look good but have noticed some deposits on the Piston. Do you think I need to replace the rings?
4. as you can see I had another spark plug break how common of an issue is this?

Dave Darling was a great help and I haven't really looked to see if he is still on here.

Here come photos

I appreciate all of the advice I can get

Cylinder bore looks OK, I would pull the offending cylinder off and lap the cylinder into the head with some lapping compound. VW/Porsche recommended not installing cylinder head seals, so that's what i did. Do you have an insert in the spark plug thread bore to use 10mm plugs instead of the std 14 mm ones ?
BTW where in Charleston are you ? I'm local and could look at your stuff.
Barefoot

Hay barefoot I’m on Johns island, the seals were to originals. Spark plugs- no it broke off I need to go buy an ease out set so I tried to tap it with a 3/8-16 and back it out with a bolt. Didn’t work.