[snowman_al]

I see it like this, I've often been wrong though.

1, Yes positive to ground for the 4.5 volt battery. It is the grid bias for the output valve and connects to grid 1 not the screen. You do need it to make the grid 1 negative with respect to the ground line.

2, no need to actually switch the HT+, once the filaments are off as long as the caps across the HT are good, there is no current flow.

3, Too many choices...

4, C3 is coupling the RF amp 1T4 1 to the tuning/detector stage 1T4 2. It will alter the signal strength to a degree. (The first stage is wide open and has no way to turn its gain down.)

5, Put the band spread cap in its central position, tune the band set cap to the centre of the band you want to tune.