On the life is about grabbing happiness where you can, and not thinking too far ahead theme, by all means grab joyful but ultimately unsuitable relationships. All part of the fun of youth. Even go so far as to marry young, if you must. Marriages can be ended. Being young, you probably stand to lose very little from an unsuitable first marriage.
Children though. Children cannot be sent back. They are the biggest commitment you can make, with another adult. You will be committed to co-parenting with their father for 18+ years, whatever else happens in either of your lives. Children do not fit the 'grabbing happiness when you can' narrative. They're great, they do bring happiness (for many / most people, not all) but it's intermittent, in amongst a lot of drudge work. They also bring a lifelong commitment and priority, that means you cannot put yourself entirely first again, for the foreseeable future.
Workwise, 1-2 years experience isn't much, if you're trying to re-establish a career after a 5-10 year absence. Get yourself into the 3-5 years bracket, with some progression and you'll be a much more re-employable prospect.
Finally (this thread has been playing on my mind a bit) your DP sounds like a very focused, successful man, who knows what he wants and when he wants it. (I've met the type. Establish career, tick. Have youthful fun and travel, tick. Gain senior / permanent contract, tick. Settle down and have family, tick). People who have achieved continuous success, worked hard to move from one step to another throughout their lives and achieved what they set out to do, commonly find it very, very hard to deal with bad luck, failure or things going wrong for them. They haven't built up the resilience on the way up that others who've struggled more, or experienced set-backs, have. If things go wrong, they panic at the unfamiliar feeling, experience and display horrible symptoms of stress and sometimes crash and burn in many ways.
I wonder if you have any idea how your DP responds to stress - that is the stress of the unexpected, the disappointing, of things not going his way? I don't mean the everyday, expected, managed stress that is part and parcel of his career.
What happens if one you is infertile, or you struggle to conceive? If you have a child with additional needs, who necessarily becomes the central focus of both your lives, for example? What is he willing to give up, to compromise on, to make family life work? To make life with you, if a family isn't forthcoming, work?
Have you ever seen him in a situation that is truly outside his control, when things haven't gone his way and he hasn't got what he wanted? How did he respond to that?
I would want to get to know him (any potential marriage partner) much better than you possibly can in a year or so, while things were going well for you both, before committing my and future children's lives to him. I'd want to know how things will work during the bad times, the difficult times, the times when compromise is necessary. When you really need to look after each other and it isn't fun. Is he the one who will do that for you? Your future children? Have you seen that quality, rather than just being told it's there?