Yeah I think that pitting will be alright. Maybe as an extreme measure you could mask up the face of the iron, and smear a little mylomar right in the seal groove to fill the pits, then the typical light coat on the fire seal and you should be fine.
I do see some pitting like that on a few irons i've used in the past, but generally not that much on one. Just like, a couple pits in one groove, and the rest is fine.
As for the boiler, the chemicals used can vary, but its generally just an industrial desgreaser thats super heated and sprayed on the parts in a dishwasher style cabinet. That pitting was definetely not caused by it
