Errm ..... if you (plural) agree what should be spent where, that sounds a pretty good deal to me. Where's the problem with something you've agreed ?
Yet in the next line you see nothing wrong in "going over budget" (i.e. breaking your agreement) and that surely sends a message to your husband that you don't actually take your joint financial discussions seriously and want to do "what you want" irrespective of the time and effort taken in reaching a so-called agreement.
I wouldn't be happy with that either. If my DP reneged on an agreement, without first "agreeing" (again) why a particular budget, was, after all, unworkable, I'd be damn angry. It would feel like my opinions counted for nothing.
I've had a relationship with a high earning self-employed man in the past. It's a cliche but remember "tomorrow is another day". When you're self-employed you often have far less of a comfort zone (than employed people) when things go wrong. Maybe he wants to keep money in the company as security against a future downturn in business, or against his own potential ill-health (insurance doesn't usually pay out 100%) ?
Are the budgets you agree hopelessly unrealistic ? ..... £200 per month for groceries, petrol, clothes (though many people have to manage on that). If so, you need to show DH a breakdown of typical spending. But TBH, I think what I'm reading here is a case of greed, not need. If these budgets were so dreadful, then why agree them in the 1st place ?
Sorry, you sound quite privileged - and in quite a secure position too (which some people will never be able to say) ......... all this "increase the darn thing" attitude sounds very petulant and I can't help but have this image of you sticking out your bottom lip and stamping your foot.