Hello,
If you choose additional custom block then related products should be displayed below this block. In case you don’t have them, please, provide admin panel access.
We checked the suggestions that you posted in topic. Some of them will be implemented in one of future theme updates.
But we are not sure if it’s useful for prefooter. If you plan to use custom footer static block you may compose footer that will include both prefooter and footer and there is no need to choose 2 different static blocks if you can show all the necessary information in one block but using 2 rows layout.
Regards