Keep working it with the dremel until you get the broken part out. Then drill it out with as big a bit that wont compromise the threads. It will come out with a little patience and finesse. Brute force won't help. Tapping on the the part, while applying pressure to the easy out/wrench combo is also really helpful.
A friends mechanic dad told me "sometimes you need to sneak up on it." It took some years and experience to fully understand what he meant. Penetrating oil needs time to penetrate.
Looking forward to hearing of your success.
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