My wife & I are retired. We are also frugal. We actually live day-to-day on our Social Security income with money left over. You asked how to stop your husband from over-buying things. I think the short answer is... you can't. He's working & he's his own man. He's going to buy what he wants to buy. From my perspective the remedy for this would perhaps be some couples counseling, or maybe more to the point, some financial counseling. Establishing a budget with some financial goals & guidelines regarding how to achieve them, that the two of you could agree on, would be the only way I could see to get some control over what your husband is spending.

You mentioned your husband has dual citizenship & is interested in moving to Europe. Perhaps the key here is for you to agree in principle to this objective with the understanding that it must be done in a thoughtful, well planned out, & financially responsible manner. Then a financial plan could be developed with the goal being for the two of you to make the move. (The two of you could, perhaps, find a financial counselor who could help you with this, if need be.) Establishing this goal might give your hubby the incentive he needs to curb his profligate ways.

If something such as this is simply not acceptable to your husband, however, you may just have to accept that he is going to do what he wants to do whether you like it or not. And, in that case, possibly what this comes down to is you seeking some individual therapy services for yourself (or using the therapy services you already have) to help you deal with the distress your husband's spending habits are causing you. There's no way I can think of to make him stop if he chooses not to.

Here's a link to an article, from PsychCentral's archives, titled "Stop Trying to Change People Who Don't Want to Change" plus a second article titled: "When You Want to Change a Loved One". Perhaps some of the ideas in these articles can be of some help:

https://blogs.psychcentral.com/imper...ant-to-change/

https://psychcentral.com/blog/when-y...e-a-loved-one/

I wish you both well...