Here's what liberated me from a similar purgatory: "Altered Scales" only really make sense when you hear them. Forget the scales, and remember that 7th chords take up 4/7ths of a tonal area; if the 9th is given, then you have 5/7ths of the equation*. There will be 2 (if the chord tells you the quality of the 9th) or three (if it is only a 7th chord as notated) notes in between the chord tones, and since in most cases the widest interval between any two chord tones is likely to be a major third, that means that there are a maximum of 3 possible chromatic notes possible between the chord tones. Find the passing tones that sound good to you. Let your ear find these in the context of the chord progression, and name the implied "scale" only after you have done this.
Let your ear be your guide at all times, then engage your brain to figure out why your ear heard things the way it did. Since music is a game of sound relationships, the ear is the horse and the brain is the cart. Losing sight of this basic paradigm always led me to some pretty rough sledding. Don't ask "what sound do really theory smart people say should sound good here in this space", but rather "what sounds do I hear as 'right', and then - if you must - why?" As always, EEMMV.
* on this point, some theoretically minded folks will likely mention scales that have more or less than 7 notes. These are by far the exception rather than the rule. I would ignore these for now and focus on the basics.
