Getting from Milan to Parma
 

This is going to be like a quiz:

If my wife and I walk out of the Last Supper at 8:45 am on a Saturday morning and hop on the Milan subway to the main terminal, what time can I expect to arrive at Milano Centrale? It looks like only a couple stops, but I have no knowledge of how regular/quick the Milan intracity trains are.

Also, once I reach Milano Centrale, how long until I can get to Parma?

Is it possible to walk out of the Last Supper at 8:45 am and be in Parma by 11 am?

If you can get the 9:20 out of Milano Centrale, then you'll be in Parma at 10:56. If not, there's the 10:00, which arrives at 11:19.

The math does not seem to be in your favor.

To make to 9:20 train by taking a Milan metro, everything must work right.

Walk to Cadorna Metro stop: ~10min
Find platform and hop on train: ~5min (assuming you already have a ticket. Cadorna is quite large)
Metro ride to Centrale: ~15-20min
Centrale Metro stop to FS train: ~5min assuming you have the ticket and you can trot (with your luggage?)

Everything goes right case 8:45+35min = 9:20. You cannot get lost and you need to have the Metro and FS train tickets already in your hand. 9:20 is a slow train not needing reservations. Taking a taxi which might be sitting in front of the Santa Maria delle Grazie church you prearranged, or after dropping off another passenger, might give a a chance to hit the 9:20 train if the morning traffic does not hamper your way.

The green line runs every 2 minutes and travel time from Cadorna to Centrale is 20 minutes.

Thanks everyone, I think I'll plan on getting to Parma around 11:30 because I don't want to have to rush. Are the train schedules I see online now set in stone or do they change as I get closer to the date?