Where can I hook up an electric choke?

As AJ said, the blue coming out of the bulkhead TO the coil resistor. One thing you could do is to CUT that wire and rig a relay in there. Trigger the relay from the bulkhead end, and hook the engine end to the load side of the relay contacts. Fuse the source for the relay off the start relay, and run "everything" including the choke off that.

There is only one "switched ignition" under the hood in "run" and that is the "normally" dark blue IGN1 or "run" feed.

IT IS NOT fused.