What is the ruling on naming someone "Saleem" (with a kasra on the letter Seen), and was this name chosen by the will of Allah, and what is the solution for the intrusive thoughts that urge changing it?

It is not advisable to keep the name "Silim" (with a kasra on the "sin") due to the obscurity of its meaning. What is well-known is "Salim" (with a fat-ha on the "sin") or "Sulaim" (with a damma on the "sin"). It is preferable to name children with the best names. It is permissible to change a disliked name to a better one. One can change the pronunciation to "Salim" without amending official documents.