How to add timestamp of N mins between photos on a video combined from photos?
Timecode isn't suitable for this. It assumes real-time footage. You can use the eif and n functions to increment the text counter to advance by 30 mins for each frame i.e.

ffmpeg -framerate 24 -i %04d.png -vf format=yuv420p,scale=1650x1180,drawtext="fontsize=15:fontfile=/Library/Fonts/DroidSansMono.ttf:text='time\: %{eif\:n*(30/60)\:d} h %{eif\:mod(n*30\,60)\:d\:2} m':fontsize=72:fontcolor='white':x=860-text_w/2:y=960" out_24fps.mp4

(BTW, framerates for image sequences should be set on the input. Using fps filter here will cause ffmpeg to drop one frame from each second.)