What would you accept in this case as the CTO?
Hold on - They are raising funding right now, but planning on bringing you in after fundraising?
If you're truly a co-founder, why aren't they bringing you in now? I'd be concerned that they're using you to secure fundraising, but they're getting the best of both worlds by waiting until after funding to give you less equity than a co-founder.
Be wary of accepting a "co-founder" position where you're being treated more as an employee. They seem to be working to cement their status as the actual founders and add you on later with an arbitrary title.
Do you know how much equity they have? How big is this "founders pool" of equity?
Frankly, between the significant salary and the fact that you're being excluded from the founder's list before seed funding, I think it's more accurate to view this position as a regular post-funding early hire. I think 5% equity is not uncommon in these positions, give or take, though you could be able to negotiate more if they're really interested in bringing you on as an actual co-founder.
I wouldn't consider myself a co-founder with < 5% equity, and I wouldn't join a team like this unless my cash comp were 75% of my market rate. If you feel super strongly about the TAM and product idea, or need less cash - take a risk! But, for me (at FAANG comp), I would need something like $175-200k + 10-20%.