I have a flight scheduled for April 8-13 SFO-EWR-MAD, MAD-FRA-SFO, that I bought in October 2019 on a P fare for $1900+

First question - UA says don't call unless you're 72 hours away. Is that still an issue. I can't imagine people are still crowding the lines for changes. Should I wait until April to call???
Second question, United has been sending me changes left and right, but the latest shows a SFO-EWR, MAD-FRA-EWR-SFO itinerary, probably because there's no EWR-MAD service. So basically, they're not going to get me to Madrid by the date I booked.

Ideally, I would cancel and get a refund, but I don't suppose that will happen, and I guess I get a credit.

I read that if UNITED cancels the flight, you get a credit and then if not used by 12 months after, you get a refund.
Would that be the case for me, since I don't have a EWR-MAD booked anymore?

If not, I read somewhere it is better to actually book a replacement flight to somewhere, since it then refreshes the use date and can be changed without fee for 12 months.

Is that the best strategy now? There's the 3/31 booking deadline for "free changes if you book now" Any reason to make sure I call before 3/31 if I want to follow this "free change" strategy?

Thanks for advice in this ever-changing refund environment.