_Question 1_ : There is a good survey in the article Constraints on counterexamples to the Casas-Alvero conjecture, and a verification in degree 12 , which gives some idea why it is difficult to prove or refute this conjecture. Phrases like "Because of a lack of a general strategy" support this, too. The conjecture has been proven for prime power degree. The smallest unknown cases are degrees $12, 20, 24$ and $28$.
_Question 2_ : An analogue for integers could start from the arithmetic derivative, which is a version of "derivative" for integers. I have not seen a "reasonable" version of Casas-Alvero for integers so far, in contrast to Fermat for polynomials, Mason-Stothers and Waring's problem.