I think that both INT2 and TMR2 interrupts should be HIGH priority.
The USART can be LOW priority, since servicing it is not really time critical.
But no, you won't be able to use DT_INTS for just the Low Priority.

Sougata is correct about the shadow registers...
They are only good for High Priority interrupts.
For Low priority ints you have to save W, STATUS and BSR in the ISR.

What are you doing with the USART handler?
Stuffing the bytes in a buffer?
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