i just got a schedule change on an award (HNL-DFW) that is exactly 90 minutes later than the original. Am I one minute off for being able to switch my destination from one city to another closer to home? DFW is not my destination.

In the case of any schedule change I doubt that AA will allow you to change airports, unless its an airport in the same geographic region (ex: JFK/LGA, FLL/MIA, LAX/ONT). To change to other than DFW would be a redeposit and needing a new award flight.

I have an AAdvantage partner award ticket that I would like to cancel without paying the redeposit fee.

There has been a schedule change; the connecting flight is 80 minutes later, i.e. the layover is 80 minutes longer than originally scheduled.

I tried to call and cancel the award, and asked whether the schedule change would entitle me to redeposit the miles with no fee. The AAgent claimed that the schedule change had to be greater than 2 hours in order to allow that.

I have a biz saver trip in April with routing SFO->LAX,LAX->LHR,LHR->AMS. AA changed the schedule of the first flight -- the MCT in LAX is no longer satisfied so for that first segment I've been moved to a flight that runs 2h40m earlier.

From what I've read here and in other threads it sounds like the general consensus is that AA can be pretty accommodating for alternatives on their own planes (assuming you call enough times to reach a helpful agent), but for partner flights (in this case LHR->AMS on BA) the alternative needs to have saver availability. Is that an accurate summation (excluding those who think AA's only obligation is to offer a refund)?

In my first call attempt the AAgent wasn't at all accommodating and insisting on saver availability for all flights (stating that revenue mgmt only opens up coach seats). Citing the schedule change and rule 80 didn't help. I'll have to see if the phrase "involuntary reroute" has the same magical effect it's had for others, but there may not be much point in the attempt if I have to wait for BA to open up the desired flight.

That is a reasonable summation.

The offer of a refund isn't AA's only obligation but it is their trump card, whether or not both origin and destination are served by AA aircraft. Is there no AA metal on a suitable schedule SFO-xxx-LHR to connect to the originally ticketed segment LHR-AMS?

So far my current revised set of flights is still the best (both in terms of duration and equipment) for connecting to the originally ticketed LHR-AMS. The other 2 options I'm considering (one via DFW, another via JFK) are roughly the same duration but I prefer them since they depart in the morning (rather than the current mid-afternoon) and would allow for a few more hours in Europe. However, those 2 options connect with different BA flights. I did consider the option of switching to the earlier AA flights and having a long layover in T5, but BA apparently has no concept of standby and I'm not a fan of their lounge for biz. I could buy a separate BA ticket but I doubt it's worth the hassle.

I noticed that BA has lots of weekend LHR-AMS availability in Jan-March but relatively little in April. TBD if availability increases within a month from now or stays low due to Easter, Spring Break, etc.