Is this given pronunciation (dubah) the usual pronunciation? I would have expected 'duvah'.
It is the correct pronunciation.
singular male = דוב (dov)
singular female = דובה (duba)
plural male = דובים (dubim)
plural female = דובות (dubot)
It's not an uncommon phenomenon, that when the vowel turns from 'o' to 'u', the following consonant gets a dagesh. Another example - yellow is צהוב (tzahov) for singular masculine, but צהובה (tzehuba) for singular feminine. A drum is תוף (tof), but the plural is תופים (tupim).
Thank you for this. Is there a rule which tells you when the vowel will change from 'o' to 'u'?
Not quite. בשביל is more like "for the sake of...", it doesn't go well with the verb לחכות.