The idiom "to be stuck/caught between arock and a hard place" means to be in adifficult situation where you have to choose between 2 unpleasant choices. For instance, if you had to choose between two jobs that you didn't like, you'd be stuck between a rockand a hard place.
習語"to be stuck/caught between a rock anda hard place (進退兩難)"是指處於需要作出艱難抉擇的情況。比如，如果不得不從兩個都不喜歡的工作中去選擇，就會是be stuckbetween a rock and a hard place (進退兩難)。
Likewise, in today's dialogue, the speaker says that Derrick would really be stuck between a rock and a hard place if his mother and wife lived under the same roof. However, luckily they don't live together, sohe doesn't have to choose between the two.
同理，在今天的對話中，對話者說到Derrick如果和他母親和妻子住在一起的話，就真的會進退兩難。但是幸虧他們不住在一起， 所以Derrick就不需要在兩方之中做出選擇。