If you are ready to move out then I would move and take the pup with you.
See how he settles.
My dogs are together nearly all the time but if one goes out after the initial whine they just settle and get on without the other one.
How far away are you planning to move? Will someone be around for the pup during the day?
You could always take the pup with you, but drop him at your mums to spend the day with Tess whilst you are at work. That way you are both happy.
If he really misses her you could always move him back in.

Really cute picture by the way, lovely dogs.

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A dog Possesses Beauty without Vanity,Strength without Insolence, Courage without Ferocity, And all the Virtues of Man without his Vices.