Agree with the consensus of others here - get to the destination, try and enjoy your trip, and deal with the aftermath later.

My last two International trips with DL have both gone sideways. Both times I was in D1, and both times had issues with a beginning or connecting domestic segment (and actually some minor delays on the TATL segments, but not that significant). Bottomline, I always have a Plan A, B, C, etc and start moving in that direction at the first hint of trouble. On one trip I had to employ Plan B and it really saved the day.

I just booked two D1 tickets for TPAC travel next February. While I know schedule changes will certainly occur, I chose an itinerary that leaves me options in case something happens.

When dealing with DL agents, it’s always best to approach it as “My flight is significantly delayed (or cancelled) and I would like to be rebooked on Flight XXX connecting to Flight YYY, etc.” That seems to make it easier as the agent doesn’t have to search for options and it’s an easy way of politely saying to them “I’ve done my homework, this isn’t my first time flying.” If you can do this over the phone rather than standing in the airport long lines of displaced passengers it generally works better. However if it’s a system wide meltdown it can be long waits regardless. Both ways you run the risk of getting inexperienced agents - so much of the experienced senior ones left during Covid. Just be polite, but also persistent and assertive in what you want.