Dear OP - you’ve had lots of excellent advice in this thread. You are in a deeply abusive relationship - there is appalling financial abuse and clearly also emotional abuse since you feel unable to raise the issue of finances with him and, in fact, since he leaves you to do all the parenting all the time. The fact that you keep saying this is his money, it’s your fault that you’re trapped and that your solution to the pension problem is to die young shows how badly treated you have been. He has ground you down and conditioned you to think not only that this is normal but that you are somehow ‘spoilt’.
It’s good to see from your posts that you are beginning to see beyond this appalling situation and plan for a different future.
Women can and do escape from abusive relationships - many of them post on MN - including one woman whose husband scarcely let her out of the house (including keeping her trapped by insisting their child be home-schooled) and had installed cameras in every room so he could watch them when he was out. She also got away.
Your children will be far worse off growing up with a father who financially and emotionally abuses their mother than being raised by you as a single mother.
Please be aware that your H’s behaviour is abusive to the entire family: you are all being abused by your DH. If this continues, it will at least leave your DC with a very unhealthy model of a marriage but the harm could run much deeper.
Since he works away so much, you have time to plan.
You should consult a lawyer to get an idea of your rights.
@Billy1966 has made a good list of the information and documentation you should assemble.
Do NOT discuss your plans with your H - he is an abuser and will likely step up his abuse as he realises he is losing control of you.
Speak to WomensAid for help with an escape plan.
If you are still in doubt as to where he is an abuser (there’s no doubt he is), read ‘Why Does He Do This’?
Be aware that, as an abuser, your H will care only about his feelings and may become expressly dangerous if he realises you are trying to leave so you need to build in some protections for yourself. At some level, he thinks of you and your DC as his possessions, to be treated as he wishes. He doesn’t see you as his equal. He won’t admit he has done anything wrong and he will fight dirty in a divorce. These aren’t reasons to stay but they are reasons to plan and prepare carefully before making your move. Also, speak to some people IRL - you will need their support.