I doubt there is any camera that meets all of your desires.
Other than the older E-PL1, E-PL2 cameras, I'm not aware of any Olympus camera with a built-in flash that tilts. And even there, I believe you are hampered by the limited flash power on the built-in flash (when you do a wall/ceiling bounce, you lose a lot of light -- so even if the under-powered built-in flash is ok for straight on shooting, it just doesn't have the power to do much of a ceiling bounce).
While there are cameras that use the FL-LM3 ciip-on flash that does flip, I'm not sure it has enough power to do an adequate ceiling bounce. Note, the FL-LM3 is much bigger than the FL-LM1 that came with your E-pm2.
You mentioned E-m10 mark II. That is a fine camera. However because it has the built-in viewfinder, it will be taller than your E-pm2. If you aren't planning on using the viewfinder on a daily basis, and have the VF-2/3/4 external viewfinder, you might want to look around for the E-PL8 which was the last camera to support the accessory port for the external viewfinder and SEMA-1 microphone. Given the E-PL8 is marketed as a low end camera, I would imagine the menu style is similar to the E-PM2, while the E-m10 mark II has the more traditional Olympus menu style. Olympus had sold a lot of E-m10 mark II's and E-PL8's in their USA outlet store as reconditioned, but lately I haven't noticed as many, so their stock may be drying up.
Be sure to try out the GX cameras in person (and then buy it from the salesperson that provided the extra service of trying it out in the store). I find the tiny GX viewfinder to be nearly unusable when shooting outdoors. I don't appear to have the rainbow color image problem some people have with the viewfinder, but with my 62 year old eyes and tri-focals, it is just too small to use on a daily basis.
In terms of viewfinder, there are 3 types. See my previous article for more detail:
I bought the E-m10 mark II last year specifically for the OLED viewfinder, and I often pick it up over the E-m1 mark I if I know rain is unlikely. It does not have a deep grip, so the larger lenses are more awkward in handling (there is a non-battery grip available, but it does make the body thicker).
Note, Olympus has new and improved the E-m10 mark III and E-PL9 models, reorganizing the menu systems, eliminating some things (like wired shutter release which instantly removes it from my list of cameras to own). The only thing that the E-m10 mark III has that is an advantage IMHO over the E-m10 mark II is it shoots 4K video, and it evidently does not have a crop factor (I only shoot 1080p video, so it isn't a feature I need -- and when I shoot video, I use the G85, not an Olympus camera).
For the 16MP cameras like the E-m10 mark II, the sensor is roughly the same as the sensor in your E-PM2. Sure there are some tweaks here and there and some improvements, but it is essentially the same. That means noise behavior will be similar. The 20MP cameras had a little bump in high ISO performance.
If you were still considering the E-m10 mark II and could have a larger budget, I might suggest looking at the Pen-F. It has a lot of 'fun' for a smaller camera, and it has the 20MP sensor. It has an OLED viewfinder so you can use it with polarized sunglasses. However, it does look like the Pen-F is going to be a one-off camera, and there will be no successor.