Reroute the track 3000’ on either side of the highway - and put in an angled bridge that is 6 times the length of the existing one.
Although doing the Environmental Impact Statement for disturbing the hundreds of fir trees (out of approximately 1.5 billion in Washington state) would probably eat up most of the budget - leaving nothing for the actual work.
Yeah, that’s the amount of work involved in making that a 100mph stretch of track. A ton of work and expense. Not much chance of it happening. Certainly not in the time frame given.
I believe there used to be two rail lines across the bridge, and they used the width of the bridge to make the curve a little gentler than it was for the one rail line.