Julia Rae, how are his numbers today? 73 and 81 area great numbers! You only need to worry when the numbers go below 50. You don't want to give insulin for numbers under 200. If your cat stays consistently under 200, like mine has after a hypo episode on Novolin, your cat will get OJT (off insulin) and you won't need the Lantus! You'll still need to monitor closely.
Be prepared that his numbers may spike up very high soon to a few days to compensate for the drop last night. That is normal. It never happened to my cat but it may or may not happen for yours.
Another thing, stick to a consistent feeding schedule and continue feeding small low carb meals. If numbers go under 50, then give honey (you can mix it in food), Karo syrup or a high carb gravy food.
A good idea is to print out the Glucometer Notes guide in the link I gave you above. That way you can refer to it quickly. It's easy to panic in a hypo epsisode but you've done a terrific job!