Amex PUJ Escape Strategy and Navigating Delta Card Upgrade/Downgrade

Hey yall. So unfortunately, I found myself in PUJ for the first time going for the elevated offer on the Hilton Business card. I suspect me opening 5 total cards last year plus downgrading my personal Delta Gold to Blue before the Year 2 AF hit did me no favors.

For Amex cards, I own just the Delta Blue and Delta Business Gold currently. I have 8 cards overall and I'm sitting at exactly 5/24 until after September.

For my overall churning strategy, I really want to use Amex business cards for say six months to avoid inquiries so I can get my first Citi card later and be open to Chase cards again sooner. The problem seems to be getting access.

I'm wondering if I put a little spend on my two current cards for a month if Amex would let me get the Marriott Business card? Or at least let me get a Blue Business card since the Blue Business offers I believe are not elevated right now.

Then I have a Delta Blue dilemma. I have about 18K orphan miles on my personal side I can't find a good use for. I MIGHT end up booking a cheap one way to MSP this summer but I'm 1500 miles or so short of that possible redemption on my personal side (I have 55K Business miles but I'd like to save those since I can't combine these two).

There's about five months until my Blue anniversary date. If I took the Gold upgrade offer now (already got this SUB so I'm willing to take any upgrade offer on this), am I correct in believing I'd get charged about $62 rather than the full $150 for five months? And if I downgraded again after 12 months but get charged the AF in September for the anniversary year, would I get prorated the $62 or so for that year?