You have something blocking the cartridge, whether it's damage from the chisel you used or some Cerosafe... A borescope will show you clearly. Looks like the damage from the chisel is still there and would block you from chambering. I'm sure we told you to polish the chamber after removing the separation.
At 4:22 you can clearly see a ridge in the chamber at the 6 o'clock position roughly I should think this is the source of your issues as Jim has said the group has probably suggested to you to polish the chamber if it was cerosafe then I gather you applied heat already to melt it but I suggest as you stated it was from chiselling it. Lee Enfields are a pretty tough battle rifle but boy that abuse they wont tolerate the ridge you have inflicted upon the chamber may now require a reaming of the chamber to rid it of that ridge as its probably past polishing.
Its better a G/S looks at it now I have no idea why those gun shops refused to look at the weapon but there you go I would have at least pressed the issue with them it makes good business anyway you have a pretty big issue now, I may be wrong it may polish out.
Go online and source a stuck case remover for a 303 Brit I have a couple of them gets rid of the stuck case POP (piece of p*ss) besides hammering the case with a chisel is just driving it in the opposite direction probably forcing the shoulder into the neck part of the chamber exasperating the condition as witnessed by just how hard you had to pound the rod to get it out.
There used to be a gunsmith worked right in both Lever Arms on Burrard St below the bridge and in Reliable gun on Fraser St. Then of course there's Italian Sports up Renfrew St. Also any of those employees are well versed in firearms and would be able to give you a better opinion from looking firsthand. I'm pretty sure one of them will have a gunsmith on the premises.
You could try a mixture of acetone and transmission fluid. Seal up the chamber end with a rubber stopper, pour the atf/acetone down the muzzle and let sit for a couple days. Stick the barreled action in an old paint can to contain leaks. The atf/acetone mix is usually 50-50 I save the larger pill bottles some of my meds come in so mix the atf/acetone 50-50 in that so you don't waste either. And yes a broken shell extractor for the 303 British cartridge is a good investment. If you do get the piece of brass out, shine a strong light in the chamber to check for damage. Some Maroon 3M sanding/polishing pads cut up and setup in a split dowel with some oil will help remove any burrs and scratches..And be sure to thoroughly clean the chamber and barrel before you test fire. Frank
Well, a G/S looks at it now I have no idea why those gun shops refused to look at the weapon but there you go I would have at least pressed the issue with them it makes good business anyway you have a pretty big issue now, I may be wrong it may polish out.