Priorities are all wrong!
Anything can and does happen to people under 30 especially at the moment. I'm guessing from op you're overly focused on a fancy wedding and not the legal - and financial - ramifications of being married/unmarried. Especially with dc involved.
Depending on where you are (assuming Uk but it also depends which country in the Uk as this can make a significant difference on inheritance law)
You cannot simply TAKE money from HIS account it's not legally yours and that would not only be theft but you'd be breaching all kinds of money laundering laws and communications laws which carry VERY high custodial sentences (mainly as these usually apply to terrorists and organised crime)
Very foolish to have dc without being married, foolish to delay marrying until after purchasing a house, marriage simplifies so much legally/financially, inc buying houses.
Aside from financially who do you want looking after your kids if you both die? I come from an abusive family and absolutely did not want them having unsupervised access to dd let alone raising her! So that was one of first things we sorted when I was pregnant with her.
none of our parents have wills or life insurance
Are they married?!
pretty much every child in the class said they didn't believe in marriage because they aren't Christian or religious etc
Marriage has very little to do with religion, for most of its history it's been about solidifying financial matters, increasing income, ensuring money is passed down to legitimate family
I do agree the realities need to be taught in school via pshe AND financial education in maths lessons. Not everyone has parents who are aware and knowledgeable or care to impart such info. In that respect I was lucky. My ex not so much. He was pretty much financially illiterate when I met him it was a lot of work to get him to understand banking, budgeting, being a wise consumer etc