Your math is off by a factor of 10. 10% of base price of $70,000 = $7000 Still as you say it won't be anywhere near that, because there's so much other stuff going on with these cars. Probably closer to the $100 range, maybe? Don't know aluminum stock prices well enough to say. It should fair better than the Model 3 which uses a lot more of the higher tariff steel, which seems likely to come in around $200 and change. Nearing %1 on the base M3 is nothing to dismiss, as that's already fighting for any sort of margin to start with.
This is assuming Tesla is buying their aluminum from overseas, which they aren't. They buy most of their aluminum, if not all, from Sapa in Portland, OR. I see they have been bought out in the last year by Hydro Extrusions. In any case, Sapa advertises that at least 50% of their aluminum provided to customers is aluminum they recycled themselves. With the tariff there will be even more pressure to recycle domestically and those companies that already do it will be in a position to scale up their existing operations.
My massage therapist's husband is an engineer at Sapa. I believe she said Tesla is one of their biggest customers. And Sapa may be getting some supplies from overseas.
I don't know where Tesla is sourcing the steel for the Model 3 (and the steel that goes into the S/X, there is some), but one of the cost savings aims for the Model 3 was to keep supply lines from raw materials to final production as short as possible. I wouldn't be surprised if they are sourcing steel from a steel recycler in the west somewhere.