Not sure if OP has shared his/her ultimate goals but if getting qualified is merely a 'badge collection' exercise of sorts, I don't think it is sufficient cause to leave right now.

Most law grads get qualified first because it is the most natural thing to do (and also since many a HR require their in-house to be qualified. This is increasingly less of a norm these days). Since OP is already in-house, I say stay on and be employed, and when the market stabilizes in (?) years... then apply for a 6 month no-pay leave to complete your TC. No rush to get qualified now unless not being qualified somehow = opportunity loss in your company insofar as salary is concerned cf. a similar level/rank peer who is qualified. Even then, the opportunity loss must be judged against your chances of finding a TC + getting retained and being remunerated decently in this climate.

I don't think part b results have an expiration date - so the above is based on this assumption. End of the day, the cons of leaving is so much more than the pros.