It's a tough time to need to contact the IRS. They're not taking calls because they're under a great deal of pressure to meet the time expectations for sending out the stimulus deposits and checks. They were given no additional personnel to achieve this and are still trying their best to process 2019 tax returns. You only have the two options to mail in the information or fax it. Mailing it cannot hurt. You were sent a form letter devised for normal times and these are not normal times. Just add a note on the cover sheet saying you are mailing in your response because the fax lines are constantly busy, but you will keep trying to fax it.
Since many other people are in the same position as you for many different reasons, the fax lines will probably continue to be busy, but there's always the possibility of getting through with the best chances probably very early in the morning or late at night.
They can indeed reduce your refund and it's perfectly legal but you will receive something and can sort out the difference with the IRS after most of the stimulus payments have been sent. Things will calm down then and you should be able to get a clear fax line and they may begin taking calls again then.
It's a very difficult time for many, many people and it's hard to accept that your choices are limited but things may get closer to normal in just a few weeks, as far as receiving stimulus checks and processing returns. Try to stay calm. Making yourself sick over something you can't change serves no purpose at all. You're not alone in your situation and things will improve.
