We are in uncharted territory here

1. It always has been the passengers responsibility to ensure they comply with the entry requirements of the destination. Yes the rules have changed but the US government set some random rules. US permanent residents are under no restriction they are free to travel to the US

2. The policy is fare difference, no refunds (unless you can use the 24 hour window in force due US DOT rules)

3. You need to ask EI they certainly know the total paid at the outset.