I understand that the Kineticist Blast counts as a weapon in certain ways and for certain feats. Given that, is there a way for me to use feats to make opportunity attacks with Blast at close range?
Take Snap Shot et. al.
There's a line of feats that starts with the feat Snap Shot and ends with Greater Snap Shot which center around making attacks of opportunity with ranged weapons. The feats can be pretty good with the right build, but you're going to struggle if you are blasting as a kineticist; consider taking kinetic blade instead, which will eliminate the need for these feats in your build.