Selling webinars with var. dates/times, need dynamic option dropdowns

Site URL: https://www.handscom.com/re-set/re-set-leading-through-change

Hard to explain, but if you go to the page you can see. Module 1, for example, is only available on 7, 8, 9, or 10 July, and the product is set up that way with variants. Yet when I choose Module 1 with the first dropdown, every date for all the modules is shown. It should show only the options for Module 1. Clearly it's not dynamically updating - is there any way to make it do this?

Time is not a problem with this program because every webinar is available twice a day at the same times, but in future we may have different times and I'll need that to dynamically update as well.

There must be a better way to sell a service like this on SquareSpace. I would also like to offer users the option of buying more than one module at a time. If they buy all 4 modules, they get a discount, but I'm going to have to make "buy all four modules" a totally separate product since there's obviously no way for them to choose their dates/times with this form.

Can anyone help? Thanks for reading!

(edit: updated URL)

(edit again: I just separated the modules, and had to hide the product used in this example. Thanks anyway.)