Money is the main cause of divorce, so I think you and your wife need to sit down calmly and talk it over and plan. Maybe do what gazabko manche said each open a separate account and have pre determined amount monthly transfer to each of your accounts from your joint account and both have to agree to be able to spend that money the way they choose no questions asked.
And I don't  think it's wise to bring out the point on who makes more money because then she may say what about all the things she does in the house like cooking, cleaning, laundry etc. he should pay her for that too.
Anyway I hope everything works out and u don't end up going separate ways just for few hundred dollars.

Having your own house for a woman is very important where she can raise her family have enough place for kids to grow up in , play. So that may be the main reason she does not want you to spend any money she wants to save every dime and buy a house soon. Maybe after that she may be more open to you spending money.

For time being just jog around the block for better health or buy a used treadmill and few weights.