Interesting idea.!
I too have been working on designs for horizontally opposed engines without crankshaft. Trying avoid the pitfalls of the scotch yoke, which is a great idea in terms of reducing moving parts but has serious mechanical impediments.
The first issue I see with your drawing/video is that the bearing on the flywheel is cylindrical. Is this where the spherical bearing comes in, but your 3D package didn't have one?
You could make a pivot for the box the bearing is sliding in.
OR !put the bearing on the end of the bar and cut a conic section track in the flywheel! This would also allow you to support the flywheel with bearings on both sides.
I see you've introduce a transverse slot in the piston rod to account for the arc of the driven pin. A vertical pin in the piston rod running in a slot in the oscillating bar might be more efficient?
Regarding valving, I think might be able to utilize the oscilating bar to come up with some interesting rod actuated piston valving,
I look forward to future installments, good luck!