Here is the math for the F# Dorian b2 mode as seen in the corresponding video below. The image below comes from the "Mode Forumula Relation to Chords Chart" from page 35 of Melodic Minor Modes In Motion (the full chart including every Melodic Minor mode is included in the book).
You can see in the chart example, the corresponding chords for F# Dorian b2 and it's theory coming from the E Melodic Minor Scale. Although the most common application of this mode is used over F#7susb9 and F#13susb9 (to the right in the "Reshaped / Respelled" box), you can also see how it is used over a F#7 chord and / or over F#7#9, F#13#9, F#7b9 or F#13b9 in the "Usable Extensions and Alterations" box on the left. This can also be seen in the Mode Chord Reference Chart below in the "Alternative Chords Box" to the right (the full version can be seen on page 37 of the Melodic Minor Modes In Motion book).