If I worry about a stuck glow plug, I'd use an air or electric impact gun on a low torque setting rather than a hand ratchet unless it is a T-bar so as to not impart any "bending" action on the glow plug. I'd slowly loosen/ tighten the glow plug while adding penetrating oil until the glow plug is fully un-threaded. The impact action really helps with stuck and rusted threads.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked