Is what I felt of comfort towards a suitor after performing Istikhara, followed by what was conveyed to me about his inclination towards strictness, the answer to Istikhara, and should I stop at that, or should I repeat Istikhara if his condition changes in the future?

The preponderant opinion is that the person who performs istikhara (seeking guidance from Allah) should proceed with the matter after performing istikhara and not abandon it unless Allah diverts them from it. It is not necessarily true that whatever happens is the answer to the istikhara. Rather, it is necessary to verify what was heard about the suitor. If what was said about him regarding extremism and radicalism is true, then it is preferable to annul the engagement. But if it is not true, or if he has renounced such views, then she should proceed with the engagement and rely upon Allah. There is no objection to repeating the istikhara. It should be noted that "being strict" (al-tashaddud) refers to excessive zeal in implementing a matter in a way that causes hardship to oneself.