If you look closely from underneath, you can see if there are eggs in the bubbles. They're tiny and opaque.

As far as introducing the pair, I always used a spawn tank. Plain ten gallon set up with a sponge filter for gentle water filtration/flow and only about 6" of water. No gravel on the bottom, so dad could easily pick up fry that drop to the bottom. Put dad in tank, and let him acclimate for a few days. Put female into a quart mason jar, and set that down into the spawn tank. After a few days when she's looking ready, release her. Etc etc etc.

I loved bettas, but eventually got tired of cleaning all those jars.

Good luck!