You CANNOT spam Soul Bombs in GQ, you can only spam Strong Attacks. Turn on Unlimited Skills, slap on Senkaizen links+Missanga and go brrr with your SAs.
The limit for Soul Bomb is 1. If you accidentally did more than 1 then quit the run and forgo it. I personally haven't mis-clicked it though, but quitting the run seemed the most logical thing for the run to not register.
Yes, wait 5 secs on the middle and hardest difficulties else the run is invalid. Easiest difficulty has no time requirement.
Highly recommended you start a dummy account to carry your main on ER; do not host public players. Or you can join the few discord servers scattered in this thread and start a session with guys there.
:)