Instead of gdybym could you use jakbym or perhaps jak bym here?
"jakbym". It may be considered colloquial, but it suits the sentence. Added now.
Feminine version? Does not specify it should be plural.
"Byłabym" and "mogła" will be needed for the femine version. Nothing specifies that 'you' is plural, "z tobą" will be the singular version.
Thank you I was unsure of this one
Byłbym z toba, gdybym mógł.
does this work? (don't have apostrophes on my keyboard)
Yes, it works. Well, if you actually put "ą" in "tobą", of course.
In another exercise, "przy tobie" was used for "with you". Is it not appropriate here?
Hmm, true... ok, added "przy tobie".