Hello
For your top speed, check if you are using it correctly:
Top speed can only be selected before cocking the shutter and you need to push the lever firmer.
If you push firmer to select 300, it's your top speed, otherwise check if you can select 500 with shutter uncocked.
Only latter Rolleis with EVS and 5 blades aperture have a speed selection independent of the cocking mechanism.
For the spacing:
The old standard doesn't measure accurately the film advancement.
Latter models starting with Rolleicord Art Deco, have a milled wheel above the receptive spool that update the frame counters.
But on the Old Standard, the frame counter is only updated when you turn the crank forward.
The spacing is highly dependent of the film thickness and the receptive spool diameter.
To increase spacing, try with a large wooden spool and the thick film.
For thick film, I can only think on Lomography with their thick cardboard backing paper, maybe you can reroll another film with this backing paper
There were actually two frame counter mechanisms on Old Standard
One that stops displaying 12, that was posted earlier by Ron
One that stops displaying a red dot
This version actually shoot 13 frames, check how many times you can turn the crank before hearing the "counter end clicks"
You don't hear it between 12 and the red dot but you hear it when you crank after
On a 13 frames counter, the spacing is very tight, expect 2mm overlap unless you use a thick film;
A larger survey must be conducted but I think 620 and 621 have the 12 frames counter and 622, the 13 frames counter
I think it was factory made.
Spacing is not something that can be changed by user, it needs some metalwork or retrofitting the other version
Here is the part responsible for the spacing, I think, since I can't find the disassembly photos of a 12 frames counter for comparison
On you film, only the first half is blank, were they shot the same day, with the same lighting conditions, it may be some speeds not working.
By the way, I hate using the red window, I simply line the start arrow with L-turn, then close the back, crank 7 times with uninitialized counter, then initialize the counter and shoot the 1st frame.