> It was hard for me to tell if he actually penetrated her
When the dog actually ejaculates you will see what looks like ladder climbing, it's all upward motion as oppose to the classic humping which is more about getting position and entry.
It does sound like your bitch has gone over, but hard to be sure with him being a maiden dog.
It is quite common for inexperienced males getting confused and stopping proceedings when you try to assist, which is why you need to teach him to accept it very subtly.
It would be best for him to be used on a proven bitch for his first time.
Next time with your won bitch I would have the progesterone tests done so you know your timing is spot on.