Hi, here's my humble suggestion until an instructor picks up:
Alternate picking does take a lot of cordination practice, so it's not supposed to be a piece of cake, keep up and you'll get there. Sometimes alternate picking is interrupted when you're switching strings, so you can land on a downstroke if going downwards or the other way round. You may try that...
Unfortunately, I cannot check if there's anything out of key. If it's a note, it may be a typo, just replace it with whatever sounds good for you as the melody is quite remarkable.
Hope this helps!