4368X2912 is very large compared to f.e. HD video 1920X1080.
If all the pictures have this large format Premiere will have a hard job to render.
You can calculate the needed total dimension by taking the zoomed in area as 1920X1080 as a starting point for the calculation.
If you have flickering you can see that on the camera monitor.
If your camera has a manual shutter speed adjustment, play with it untill the flickering disappears.
A 2 sec difference in sync can be caused by a dropout in the tape, special with HD recordings. You will have less problems if you use HD mini tapes. They have a better quality on dropouts.
We have correct this by unlinking video and audio and moving the audio in the right direction (re-syncing)
The audio will be mono. Track 1-3 are stereo. By putting the file on the timeline a monotrack 4 is made.
I don’t see any problem to keep your sound on track 4.