The outlet voltage is fine, and will fluctuate depending on load during the day, so you can read anywhere from maybe 112V to 122V at various times. I don't have any experience with your model, but Seth here at Fixya answered a question about the oven not going higher than 250 V for another person. Here is his answer:
seth765
Rank: Guru
Expert
Rating: 89%, 266 votes
this is normally a faulty electronic control board and should be replaced.But you can check the resistance on the temp probe
That it is the electronic control board makes sense, since the potentiometer for the coil voltage is there.
As for the button problem, the display assembly would have to be taken apart to see exactly what is going on, I know that from having been an electronic tech all my life, and I've had to fix all my appliances myself. Being that way, I would try to get at the control board to see if there isn't any corrosion on the gold-plated contacts that switches use. Sometimes their construction is such that you have to partially destroy it to see what's going on. Service techs don't go that far, they just replace the part, which is what will be required of you, most likely. If you do try to get inside to check it out, make sure all wire connectors are tight and not loose. If you can get some electrical contact spray cleaner inside the part, try to spray the switch contacts, operate them, spray some more, and let them thoroughly dry. Don't work on the unit unless it's unplugged. I wish I had an "easy fix" for you, and maybe I could figure out one if I could see the unit, but that's all the thoughts I have on it. Replacement of the panel may be the only option, sorry. I guess you could get them a repair person to give you an estimate first, but they'll be expensive, and you end up having to buy the part anyway, in most cases. Good luck, hope I helped some.