Overpressure in the cylinder head.

Is it poosible to have overpressure in the cylinder head due to stalling, jerking during towing?

No. Sounds more like a lean condition. My experience with these engines is that they aren’t very strong, so if your towing with it your abusing it and it won’t last long.

In the days of poor quality gasoline and misadjusted carburetors it was possible for the compression in a cylinder or multiple cylinders to increase because of carbon deposits on the tops of the pistons and in the combustion chambers. This would be going back to the '50s and earlier and is unheard of today. The symptoms you describe are not associated with this phenomenon but hard starting due to the starter being unable to properly crank the engine was a symptom. Hope that helps! Jim