On a previous post, you mentioned you have a SW Premier Visa (I just did a search on this thread, I'm not a stalker). Did you cancel that card? Because you can't get another personal SW card if you currently have one, since in April this year Chase implemented a One personal SW card rule. So I'm going to assume that you did cancel it...
Beyond that, is $750 reasonable? Well, you would get over $2900 of SW airfare plus whatever you want to value the CPs at. If there's a way to reach the MSR without incurring those fees that would obviously be a more financially sound choice. $350 in fees for how much in spending? The $8K MSR on 4 cards? That works out to 4.375% in fees. Did you know you can pay federal income taxes at 1.87% fee on a cc? That's even lower than Plastiq, which charges 2.5% fees, and can make almost any kind of bill payment you'd want. Visa technically doesn't allow mortgage payments but some have had success working around that in Plastiq. Tips are in our Dischurners reddit, as well as support links.
Since the SW Biz doesn't count towards your x/24 status (but you need to be 4/24 in order to get it; same thing for the CIP), you would want to apply for the biz card(s) before the personal card if you're nudging up against 5/24.
My SW CP runs out at the end of this year. I plan to apply for the SW Biz card at the end of this month but not put any spend on it until January, then one of the personal SW cards in Feb 2019 when I drop back to 4/24. I hope to have the CP by March.