Can I claim a deviation ticket within 3 days of the end of a trip between two unrelated cities? (For example, Trip ends in ATW, Jumpseat back, then buy a ticket between DFW-ATL 2.5 days later, where ATL is home) I suspect the answer is no, but the wording in 8.C.4.e says "...and must proceed TO the intended destination of the deviation..." it doesn't say anything about originating in the intended destination.
I deviate a lot of trips on the back end that go home instead of Mem. None of them "proceed to the intended destination."

Yes. This is a common type of deviation. Trip ends with a DH, you go home, not to domicile. As noted, be careful how long you wait, I believe you are right in having three days, but I'll let someone else reconfirm. I'm fairly certain it is no longer than three days.

I have done that in the past with no problems.

5million, yes you are allowed to do that. I too have done this numerous times. I often jumpseat down to Houston to visit my folks, stay a day, and then use a ticket to fly home from there.
BTW, the "travel within 3 days" in the contract has been interpreted by crew travel audit to mean 3 CALENDAR days, not 72 hours from the end of your trip.
But, like all questions that involve deadheading legalities and monies, when in doubt, ask crew travel audit and contract enforcement. DO NOT depend on advice from these boards to make decisions that involve legalities with the company.

Thanks fellas!

Slight hijack.

I want to expense ground transportation from home to Fedex facility then jumpseat to Memphis (domicile) for recurrent training (CLOE). Is this an allowable expense? I do it all the time for trips, R days...but what about recurrent training?
8.C.4.e says "within 3 days of the scheduled assignment to/from which the pilot is deviating (e.g. Scheduled deadhead, trip or R-day)
Is recurrent a "scheduled assignment "? Anyone have any experience?

Yes. Essentially if it is on your calendar you can expense a legitimate travel expense to get to the activity. Outside of your base of course.

Is that a taxable event since it is not a deviation and you are traveling to your base?

I select yes.

I've heard it is correct to select "no" on the GT because it's between home and Fedex facility (not domicile). If you GT to pax airport and Pax DH on paid ticket then it's "no"(GT) "yes" (ticket)