Although a devout believer he didn’t share devaleras belief in the need for church supervison over aspects of life
A greater, opportunity for the mother and child health bill.
He already was "Prime Minister" before his death as "Chairman of the Provisional Government", post that it would depend on how CnaG developed post Civil War and the nation.Might he become Prime Minister or President of Ireland at some point?
Personally, I think that it would either be Collins or Dev because the spark for the civil war was over the treaty and if Collins were to live and win the civil war then 1. Ireland would be a Dominion and 2. Collins would be the Prime Minister of the Dominion of Ireland. That's mostly because Dev was unyielding in his unwillingness to compromise, and if Collins is to be relevant in this TL, Dev loses and possibly dies.
I don't think it's very likely that De Valera would be killed. But he wouldn't be as powerful as in OTL. He would still be a major rival of Collins, and it's possible that either he or his allies take power in the 1930s. But in both the short term and the long term Dev's status would be reduced if Collins lives to be his foil. It's less likely that he becomes Prime Minister or President for example.