With 150k actuations I wouldn't bother with repair. You've already figured out the K-3ii and KP strengths and weaknesses; only you can decide if the single card and different battery are acceptable to get the KP's better noise and AF.
I wouldn't rush out to buy the KP tomorrow; allow time to get familiar with a new camera before using it for a paid shoot. Therefore, since you already have a familiar K-3ii and K-30, get by with that combo for tomorrow. You'll then have 4 weeks to order a K-3ii or KP+grip.
With respect to your malfunctioning K-3ii, I don't expect any of this to actually fix it, but it's free to try:
- Try shooting without a memory card. Maybe that will trigger something in a different way and let you get into the menu, then do a factory reset.
- Try a soft reset by leaving the battery out for a few days. I think 3 days should be enough but I'm not certain. When you restart it would normally ask you to enter the date and time. See if that's enough to get things to start responding.