Genie+ rarely sold out except for extremely crowded days. You can buy it starting at midnight the night before, IIRC, but that won’t help you if you need to see how your husband is feeling before booking. You cannot start booking rides until 7am the morning of.
If you are looking for low key rides hopefully it won’t matter if you aren’t logged in exactly at 7am. For headliners, it can be a different story.
You *should* be able to book at 8am and then beginning 2 hours after park open, but don’t quote me on that one. We are among the ones that have multiple alarms set just in case. Booking Genie+ rides has kind of become a game.
One other thought - is it just the 2 of you or is your party larger? If he isn’t having a good day does everyone stay behind or just him? Because if others will be going to the parks regardless of how he is feeling, you may want to start at 7am anyway, and then just write off the cost of his Genie+ if he ends up not using it.