OP, you need security to allow you to become and remain well. Health is more important than anything money can buy.
IMO everyone who can possibly afford it should have at least a six-month buffer in the bank. It reduces stress sooo much, knowing you could pay the bills for that long if something terrible happened. It buys you thinking time, recovery time, planning the next move time.
I think you should stick the £30k in a fixed-term high interest account. Maybe a flexible access one - the sort that you can access 1-3 times within the fixed term, if you need to.
Your DH is very muddled about money and doesn't seem to understand the difference between capital and revenue. Revenue is what you use to fund your outgoings, including building up new ventures. Capital is what you invest - safely.
Think of it this way, how long would it take you to save £30k? A long time. If you want to spend the £30k, the only sensible way to do it is on things you can keep (and won't be taxed on) e.g. your own home. Even then e.g. if your were extending, you need to do the sums and work out whether you would really increase the value of the house that much, you could well not.
If you were to visit an IFA to discuss investing your £30k, what are the chances they'd advise putting the entire sum into an unproven, small, local business with a very poor track record? None, zero, nada, zilch.
Funds for business investment need to be generated from the main business's success. Saved, grown, matched by reputable loans if needed and successfully obtained.
By all means cut back on the expensive hobbies and outgoings, save the money to plough into the business and grow it that way.
Your DH sounds like someone who thinks he can have it all and have it now, just because he fancies himself a businessman and aspires to a lavish lifestyle. No mate. That's called living on credit (that you've no reasonable expecttaion of paying back). You sound like someone heading for bankruptcy.