Sorry if I'm a bit too late to add some advice here but I'll offer you this:

A 3 even a four stop push isn't horrible, in fact it's doable. Ektachrome isn't completely unforgiving. I'd start by placing the film in a plastic bag in your refrigerator until you can get your own E-6 kit from an outfit in the U.S. like B& in New York. Or send it to a Kodak Q lab for processing. With a large note that asks them to SNIP test the first several frames with a 3 stop push and ask them to determine how to process the remainder of the roll based on the snip test and that you shot it at ISO 1000 not 100. That should help out a lot.

Worse comes to worse, you'll probably notice some muddy exposures, a significant amount of grain from the lengthing of the processing, but you might actually find some interesting results.

Also, once your film is processed into the ballpark that the snip tests determine would be about right, leave the film unmounted and then if you have some nice shots that need fixing, have the same lab use some kodak duplicating transparency film to make some additional exposures to improve on the exposures they already have on the originals and boost up some of the detail, help the contrast and maybe give your shadows less muddy appearance.

Take care and good luck. Don't be too hard on yourself. It happens to the best of us you know.