Looks to me like it was 32000 feet, 469 knots.
Would it be possible for some other craft (or a missile!) to have gotten out there without being noticed on anybody’s radar?
That's what I see when I play back the FlightRadar24 feed (not 750 feet!).
If this other report of the pilot requesting a climb on his last transmission is true, then that's also consistent with weather avoidance. An A320 loaded with only passengers and their luggage is operating at a fairly light weight, and is likely capable of climbing up to 36,000 feet, at least, if they needed to do it. That would be consistent with attempting to clear the tops of the cells, to stay out of turbulence, and to stay visual with the active cells to avoid them.