I hate to rain on the parade but it sounds like you're right to be questioning his lack of enthusiasm. Even if emotional displays are "not his thing", there are some things you should expect if he really loves you and is really interested in a marriage. The thing is, most men will avoid conflict at all costs and even though you haven't "held a gun to his head" he realizes that this is what it's going to take to hang on to you. You are his comfort zone and sometimes, for some people, being with someone for the wrong reasons is better than being alone for the right ones.
The real question you both have to ask yourselves (and you may have to ask his for him) is Do you both feel like you're getting exactly what you want in another person, or are you settling for what you can get? On a second marriage you should also both realize that it takes a lot of work and a lot of real, true love to make it work (along with the desire and dedication to make it work). Marriage is serious, nobody takes it seriously anymore but what would we all do if there was no divorce? What if you had to be joined with this person for the rest of your life, period? Would you marry him anyway? What do YOU want?