You didn't mess it up yet. Keep cutting all that metal on the oil compartment away.

You will end up with just the crankcase when it's all done.

Look at the front and rear bearings. Look at the crankcase around the bearings and try to imagine the crankshaft counterweight inside there. It's probably about a 2" or 2.5" counterweight. Look at the diameter of the crankcase around the bearings.

In the last pic you posted--look up inside that hole on the left side. You still have an inner wall. Thats the crankcase. Keep cutting.

All that oil compartment is for is the bar and chain oil. It's not connected to the insides of the engine in any way. Probably got a gas tank on the other side that looks real similar. The engine oil would have been mixed up ahead of time and just poured into the gas tank.

All you got right now is you've gotten inside the bar oil tank. The crankcase is still further inside. Keep cutting. Go slow. Once you get some more of that metal off it will become very clear where the crankcase is.

Be careful around that carb and the spot where the reed plate goes on. It's going to be a tunnel where the fuel flows into the bottom of the case. Don't get in a hurry and cut into that tunnel.

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Edit:
Look at your first pic in the last post you made. Look at the crankshaft where it comes out of the case. See that round circle about 2.5" across? Thats the crankcase. You haven't ruined it yet. Keep going.

That case has a left half and a right half. One side of the crankshaft used to have a magneto on it. The other side of the crankshaft had the clutch and sprocket on it.

The bar oil tank was in the front and probably driven by a worm gear. Fuel tank was in the back of the motor.

There's a left and a right side of that case. When you get done--you'll have a front half and back half of the case because your turning the motor forward to spin a prop. Look how the case is joined together. Screws go through one side and thread into the other side. Don't cut the screw holes away or you'll never get it to bolt back together again.

Cut off all the gas and all the bar oil tank. Should be nothing left but the crankcase and the screw knubs when your done.