By filing the foot spring on the detent thinner, I got it so that 2 lb tangential force on the center wheel got the clock to run. Still way too much. So I kept filing, and the spring got very delicate. I didn't break it, but it was no longer stiff enough to stay vertical. So, time to make a new detent.
Figuring that detents were delicate, I made two: a spring one like the one I over-thinned, and a pivoted one. The pivoted detent consists of two parts, a pivot, which attaches to the cock, and the detent itself. The detent has a counterweight instead of a return spring. Here are the parts, with no springs...
... and here is the pivoted detent assembled.
It wasn't hard, but required a little thought. The pivoted detent is much easier to adjust, but even a bit too light. A few tenths of an ounce on the counterweight seemed to help. But I broke the pivot hole, so I'll need remake it.
As for the rest of the clock, the idea of a 4-second period for a compound pendulum with a small radius is not going to work. The longest I can get is about 1.5-2 second period with no escapement in place. So this means the gearing will be all wrong... Perhaps this clock too will be a timer.