His future self opens a window and says “Hey, get some paper and a pen, I’ve got some winning lottery numbers for you!” and his past self goes “Oh boy!” and then immediately CLICK (closes the portal) before ever being shown the numbers.

Here’s your issue - it’s not the future self opening the window, it’s his past self. The future self can only speak through the window, but he can’t open it. So since the “current” self closes the window, the future self won’t be able to speak through it.