Practice analysing the excerpts you receive without using the sound and only using the score. You can answer most of the questions by just looking at the score. You can use the sound to relax and check what you're saying is correct.
For the melodic dictation. I am also terrible at it. But here's the method I like
1. Draw the melodic contour above the bars or on a blank page. That way, if worst comes to worst, you can guess the notes and get the marks for correct contour.
2. Think in leaps and steps. Make a small mark on the page if the notes are clearly more than an interval apart or only an interval apart.
3. Get to know your intervals well
4. Don't stress about minor inaccuracies. You're guaranteed 3/5 if you notate pitch and rhythm with a sense of melodic shape and rhythm. You can get 5/5 with "minor blemishes"
