If you both have an AGR account, and you've provided your numbers, then both of you will get points for the railfare portion of the tickets. That's the base fare to get from A to B.

Whomever's name is listed first on the reservation however will get all the points for the money spent buying the room. That amount is not split. So you may or may not wish to list each of you first depending on how you wish to spread the points around.

If you sign up right now and call up Amtrak and have an agent put your number into the reservation, it may not be too late for you to get points automatically. If signing up right now is too hard, do it within 15 days as you can then call AGR and still get points for this current trip.

One other thing, as long as your husband was registered with AGR at the time he took the trips, you should be able to get him credit for at least some of the trips where he failed to provide his number. I'm not sure how far back they'll go, I'm thinking 90 days but please don't quote me.