Sorry but I can't see the logic behind this person suddenly becoming a director and being given 50% of the shares. Is he bringing investment? Skills? Why exactly is he being given 50% of the business including its assets (at your expense)? Is he going to work for a period of time for the company to see if it's a good fit before he is given 50% ownership?
If something was to happen to your husband, you would have to wrestle with a stranger about anything to do with the business, from the most basic information to to the biggest decisions.
Again I really think 50/50 split in shares in this case is a very bad idea, because no one has a decisive vote.
If something was to happen to this new director, do his shares reverse into you/your husband ownership? Do you have to buy them back from his estate? Can they be sold to yet another third party?
Even if it is your husband's business, if you are married without a contract and the company was started whilst you were married, it is 50% yours.
If you are no longer a director, and don't have shares, technically you have no means to do routine checks of the company's accounts (you can go on Companies House but the info will be yearly and not up to date) and you cannot make any decisions for the company.
I completely fail to understand the logic behind divesting you of your shares to give them to a third party or how you would benefit from that at all.
You would not longer be legally responsible for the company but that doesn't exempt you from all responsibility. For example if your husband owed money to the company, you would be jointly liable.
it's a good thing that you have some form of control over the business, I wouldn't let it go to a third party unless there were very convincing arguments. It all sounds a little weird OP.
It irritates me when men use their wives names and legal entities when it suits them/their business but still think that they can do whatever they want, including taking it away.