Alright, I again tried playing in 4K with Ultra settings without trainer, everything worked fine. 4K with trainer it crashed every time, or soon after, something was activated. Set it to 1080p on ultra settings again and it works flawlessly, 3 hours no crashes with unlimited movement, invincible army, 1 turn reforms, unlimited ammo, refill army and a few others used.
This is because you froze the option. All you need to do is edit it to 990k, hit enter and click off. You'll get the gold. You don't need to freeze the value there as that freezes the 'current players' gold to that value. You do it on your turn you're ok. If you end your turn it cycles through everyone else, giving them all 990k too.
If it's YOUR TURN and you don't press END TURN and you DONT LEAVE OPTIONS ON, then should only be for YOUR FACTION.
Unlimited Movement has MORE OPTIONS setting. Set the value to a lower value and see if this helps in 4K. Maybe the game is trying to display more than intended due to the way the trainer is allowing units to move long distances.