Make sure you understand the T's & C's of the warranty. Like do you need to bring it to them every 6 months for a fluid change to keep the warranty in place? You'll go broke doing that, lol.
No way the TV cable misadjustment burned up your clutches that fast. But it sounds like they made it right. The kickdown band being too tight shouldn't really adjust the shift point. All that adjustment does is set the resting drag of the band on the drum, which effectively sets the required servo pressure to lock down the drum. It would make the shift firmer, but not sooner. The TV cable, governor, & valve spring stiffness will affect the shift points. And I guess the line pressure screw, that you normally wouldn't touch unless you had established that the pressure was out of spec.
To take the tv cable out of the mix (to a certain extent), just shift manually and see if it performs like you'd expect. If that's fine, but shifts early when in D, it's almost certainly the TV cable adjusment still. I fought with mine for a long time after I replaced the OEM cable. But it's finally fun to drive again.