You may find better answers in the Mazda area, but here's what I have to
offer:

You need to be able to determine whether the engine and transmission are
each operating properly, independent of one another.  This means you need
to find out whether the engine is delivering normal power, whether the
transmission is slipping, and whether the torque converter clutch engages
and stays engaged or is slipping.  If you cannot feel these things and do
not have the tools necessary to monitor them, you'll need to take it
somewhere qualified to do a proper diagnosis.