Yes, he has a legal right to the money you have been stashing away. Money you have spent hosting his family has no bearing on it in any state of which I am aware.
During the divorce, you will be required to do a discovery process in which you state all assets and turn over bank statements. It is very likely that your subterfuge will be discovered at that time.
If the judge determines that you have been deceptive, there is a high likelihood that he will punish you by giving your husband a disproportionate share of the family assets.
What you are doing is a bad idea. While it is possible that you will get away with it, it is more likely that it will backfire on you badly.
Hmmm, since it's coming out of your paycheck his side will figure it out sooner or later. Someone will notice the missing $ from a total, OR see a pay stub and ask where that $ is going.
If you don't have a lawyer then perhaps you can use that $ for their retainer. They can't claim half of what isn't in the account.
If he spent a bunch of money on stuff and ran up debt today, you'd be responsible for half of it.