[nkaminar]

If the engine bogs down when you pull down on the timing lever then either the timing is way too advanced or there is a fault with the distributor. I know you said that you have checked the ignition system, but it is still ignition related, so something is still wrong. Pulling down on the timing lever will advance the timing.

Check to see if the top plate in the distributor is not loose so that when you move it the point gap is changed. Also check that the wire that leads to the plate underneath does not have a bare spot that is rubbing against something.

The timing method on a Model A is pretty fool proof. Assuming the cam is timed correctly, the points should just be opening when the timing lever is full up and the timing pin is in the detent. If not then it is not timed correctly.

Lots of people use a timing light and degree wheel on a Model A to check the timing. The mechanics are the same as a modern engine. You can buy the parts from the vendors. Instructions come with the parts.