Your new camera has 3 times the resolution of the old, which would explain the lower framerate.
You could create a RAM drive and save the video to there, before copying to the SD card. Either that or try getting a high speed USB3 memory stick such as the SanDisk Extreme models and save to that.
I did exactly this last night and it worked OK.
I have has some FITS images without WCS information embedded (entirely my fault) and I managed to update the files by loading into ASTAP, solving and then save new header. The images can then be loaded into the FITS Viewer and used to center the telescope.
I'm having an issue with capture on my Olympus E-M1 Mk2 that I hope someone can help me with. The camera is detected correctly in the INDI server and I can see and configure all the settings such as ISO control.