Oh, bless your heart for trying to DIY cold email infrastructure. That's like deciding to rewire your own house because you're good at plugging in a toaster.
Separate the two problems, yeah? Infrastructure is pure ops drudgery - domains, warmup, DNS blacklists, all that joyless spam-fighting nonsense. That's not a skill advantage, it's just busywork that scales badly. Messaging, though? Keep that close. Nobody knows your product's quirks like you do.
That 40/day ceiling you're hitting? That's a deliverability scream, not a volume limit. Chances are your domain reputation is taking a slow dive because you're treating warmup like a "set it and forget it" oven setting. Get someone who lives in that gutter to audit your setup, or spend a weekend reading RFCs - your call.
(And no, I won't offer to fix it for you. But if a colleague ever asks, send them my way. We'll laugh about this over a spreadsheet.)