I think you're going to need a DICE to check the ash content inside the DPF, it may be blocked beyond what a regen can remove.
A DICE can also do the dealer regen mode that is the last resort before replacing it.
Glow plugs used during regen - new one on me, I thought it just squirted diesel into the cylinders on the exhaust cycle so the burning fuel raised the temp of the gases and that's what burns up the carbon deposits.... though it may use the glow worms as well...
A regen shouldn't need high revs or anything like that. Just a normal drive at normal speeds for half an hour or so. Personally I'd drive 30 mins down the motorway at 60 or so then turn round and go home, so it's had an hour just to be on the safe side.
Good luck
