I'm glad the conversation went well and I hope it's the start of many so you can fully delve into the topic. It's great that you are taking a thoughtful approach to this unexpected news rather than wearing rose glasses (and either assuming the money will be yours or that it won't affect you at all). The stories above about the wealthy one wanting to spend more or wealthy in-law expectations are very illuminating. Talk as much as you can about how you'll handle things, such as vacations or home repairs/renovations.
For one more prenup story, a friend of a friend got married to someone with a well-known family business. They dated for many years beforehand, during which she supported him financially through some failed business ventures. He presented her a last minute prenup within weeks of the wedding (but not so close as to definitely trigger legal issues regarding consent), which really pressured her to sign quickly. However, he just threw up his hands when she wanted to negotiate any of it, saying that the family attorney drafted it and he wasn't responsible for it. It didn't even seem as if he had read it. What was the egregious request she was making? They wanted a bunch of kids and for her to stay home with him - he was *very* traditional. She had healthcare concerns, which she was worried that pregnancy might exacerbate. She requested that he commit to covering her healthcare for a limited time (~1-2 years, I don't remember) if she quit her job to raise kids, as it would likely take her time to get a new job afterwards. This is pre-ACA days. Note that she was not even asking for compensation for lost earnings, promotions, retirement savings, etc. He refused, citing the family wouldn't let him change the prenup. My friend suggested to her that if she signed as is, at the very least she get a postnup before quitting her job. She married him anyways. At his behest, she quit her job - without a postnup. In a short time (I don't recall exactly) they got divorced. Luckily, her job loved her and hadn't yet filled her position, so they happily took her back and she didn't have issues getting healthcare coverage.
So...the moral I take away from this is that you should have these conversations early. If both parties aren't willing to look out for each other when things are at their best, they are unlikely to do so when things have broken down. To look out for him, you can offer a prenup. Hopefully he will be reasonable as to what he offers to look out for you, if your choices as a family negatively impact your wealth-building and independence. But also be kind that he may not know how he feels or will handle the money if it is new to him and it may evolve over time.
And as to the ~20% for 10 years idea, I've always hated those cliffs because you read about all the news stories where people divorce 10 days after the cliff. If you go that route, perhaps something more graduated so there is nothing enticing you to stay for a specific time (e.g. a % each year staying home with kids)? Presumably he doesn't want you to stay married simply for the money either.