If it's the sumatriptan injector (Imitrex) that you have, you can split your injections to use less and still get the same results. https://clusterbusters.org/forums/topic/2446-extending-imitrex/
YES, get that oxygen. Changes everything. See the overview file linked to in the last sentence below for more info about getting and using O2.
Are you doing the whole D3 regimen? https://clusterbusters.org/forums/topic/1308-d3-regimen/
Was the loratadine (Claritin) prescribed, or did you decide to take it? (It's a good idea; I'm just wondering.)
If you're not taking the full D3 regimen, you don't have a real preventive medication. That's what the Depakote would be for. I don't think Depakote is prescribed much anymore (side effects, I would guess), but it was fairly effective in small clinical trials. If you do the full D3 regimen, you'll get the prevention without the side effects. I take it you haven't tried Emgality or one of the newish CGRP medications?
Since you're new to this thing, you might get some thoughts from this overview: https://clusterbusters.org/forums/topic/6213-basic-non-busting-information/