The Chase Ink you have is the Ultimate one or whatever where there's an annual fee right? Only other thing about actually acquiring the points is meeting the spending requirements (esp the $4000 in in the first 3 months - and I'm assuming the points wouldn't be credited till *after* you meet the requirement). Not sure what the 'easiest' way is to do that via manufacturing spending.
I always thought credit scores would be affected by closing cards in general. But I guess there's other criterion that affect your credit score, like utilization per MrSal. I find it odd that you say you've closed so many cards in the past two years with absolutely no effect on the credit score. I think if you downgraded them that would make more sense but if you actually closed the account(s), wouldn't that affect your score in some way/shape/form? Maybe I'll look into upgrading to the CSP instead.
If you can't meet the minimum $4K spending, defer applying for the card. I looked around for $3K offers, but they're no longer available. Manufactured spending is still possible, but getting harder, so you may want to test the waters before making a commitment.
The only (current) way that closing a card would affect my score is if it were tied to my utilization ratio, i.e. if I kept an open balance. Your score isn't affected by closing accounts in good standing.
To my knowledge, upgrading to the CSP won't net you the 50K UR bonus, so don't bother unless you can confirm otherwise.
Additional rules: Chase has applied the 5/24 rule for their cards. This means you cannot have opened more than 5 new CC accounts, from any bank, within the past 24 months. Based on your questions in this thread, I assume you're okay, but thought I might as well point it out. Otherwise, if your credit score is in the high 700's and you can meet the minimum spend, the CSP is generally a good value.