Make a list of distinct positive integers that are obtained by assigning a different decimal digit from 1 to 9 to each of the capital letters in bold in this expression.

(A+B)^C + (D+E)^F + (G+H)^I

Determine the smallest and the largest positive palindromes. What are the smallest and the largest prime number? How many amongst the abovementioned list are tautonymic numbers?