I don't think valve will change the price due to tariffs. The deck was originally sold at a major loss to reach valve's target pricing, and they can afford to lose money on it because it drives game sales.
The deck has sold a lot more than expected, which has brought manufacturing costs down. I suspect the Deck is fully profitable now, but if tariffs make it unprofitable again I'm pretty sure valve would rather eat a loss on the hardware and keep enjoying the increased software sales per steam deck owner.
According to protondb, you need to replace the EA app with origin.
Check the second review by "L4ZaRu5", it has a guide.