Yes, Celebrity Cruise.

I cannot help with your core question, but two observations:

1) Near as I can see there are no nonstop flights between VCE or FCO and DFW, which means you will need connecting flights. Connections could be made in USA or in Europe.
2) Even in normal times, schedule changes are likely when booking a year ahead, and this can easily disrupt connections. I think this is even more likely as airlines adjust to variable demand affected by the pandemic.

I would choose a schedule with a buffer day (or more) on each end to allow for this.

I would definitely see what the cost/options of adding air via the cruise line is. The key benefit to that is not having to worry about missed connections as far as getting to the ship. The cruse line option should guarantee transit to the ship, even if you misconnect. You can save money doing flights yourself, but you are on your own if you don't get to the ship in time for departure. I don't know what type of insurance one might get that could possibly cover "catching up" to a departed cruise. Finally, you may have the option of upgrading the air option that the cruise line provides to J or F, though not by use of Chase points....unless the flight is on an airline that allows Chase point transfer (UA, BA, etc) and a subsequent point based upgrade.

It�s easy to take the train up to Venice from Rome. TrenItalia can zip you up there many times a day on the red line. Keep that in mind if the flights to VCE are troublesome