The general advice about O2 is to keep inhaling it even after an attack has been aborted, 5 minutes longer, or more. That can help prevent or minimize subsequent attacks.
It's a bit surprising that a sumatriptan tablet is helping you, since many people find that tablets don't work fast enough. Nasal spray or injectable are more effective. You can split the 6mg injections so you get three aborts from them, which reduces the overuse concern and of course makes those expensive injections a little more affordable.
Regarding the verapamil, that's a relatively low dose, and you should be using the immediate release kind, not the extended release kind (can't tell from your message which you are taking). The vitamin D3 regimen is a better and safer preventive than verap. You can read about that, and some other information and tips, in this file. https://clusterbusters.org/forums/topic/6213-basic-non-busting-information/