Several Considerations
There are several different considerations here. If you were flat betting $50, then I think it find it more useful to use the coupon when you don't have an edge on Insurance, and to buy insurance money with your own money if you do.
Consider this example. You have two possible insurance bets to make: With one, the Probability of winning is 34%, and with the other it is 35%. Suppose you decided to use the coupon for one, and bet your own money for the other. Two choices as to where to use the coupon: for the 34% bet or the 35% bet. If you compute your total return from both, I think you will see that you would do better by using the coupon on the 34% bet, and making a conventional insurance bet for the 35% bet.
Similarly consider another example. A negative EV insurance situation with a P=30% and a positive with p=35%. Two choice: One is to use the coupon for the 35% bet; the other is to use the coupon for the 30% bet, and your own money for the 35%. I think you will see that it is better to use the coupon for the 30% bet.
However, I was assuming that all the wagers were $50. In your case, some of them will be smaller. We can run some numbers but my strong gut feeling is that you should use the coupon for the full amount. Don't waste it if you can only make a $15 or $20 insurance bet.
The simplest strategy may be to flat bet $50, and use the coupon for first Insurance opportunity where you would not buy insurance with your own money. This may not be perfectly optimal, but additional improvements aren't going to get you that much more money.