I guess your options will depend on how much of the key is in the lock. If you can see the broken end, you're off to a pretty decent start. If you can't, you're going to struggle.
Here are a couple of images of the CA77 steering lock:
I'm not sure where you're referring to when you say you're trying to put something in above the lock to try to knock down the pins, but I suspect it's the flat section you can see in image 3. If that's the case, it won't work 'cos the pins - assuming there are any - are inside the assembly. I say assuming because if the lock mechanism is anything like the seat locks on Honda's of the same age, there are no pins; they have a barrel with internal shaping (they're pretty crude). As you can see, there's a locating pin that sticks out when the lock is turned; that's the bit that may be preventing your lock from coming out. The key (and pin) needs to be in the 1-to-2 o'clock position to free the lock from the frame; the key will only come out of the lock at the 12 o'clock position.
Again, how to remove the stuck bit is all about how much of the key is in the lock and how you can manipulate it. If I were you, I'd try to remove the key piece first; worry about getting the lock out later 'cos you can get a duplicate key if you can read the lock number. If you can see the broken bit, first try to turn it so it's in the 12 o'clock position - that'll at least give you half a chance of getting it out. Unless it's been jammed in and has completely frozen the mechanism, it shouldn't be too hard to move using watchmakers screwdrivers and sturdy tweezers. Bear in mind the key part in the lock will only be around 1/2in long; there's not much to it and it won't have a complex set of teeth. The same tools can also help you pull the remainder out. I've also extracted broken key parts using those tools and superglue before.
Does that help?