Sounds like you are a candidate for a trike! But seriously, I used to have a
Toureasy and found that anytime the front wheel encounters any slippery
surface, you will probably go down. I replaced the stock tires with a
Schwalbe Marathon front and rear. Once I had the Schwalbe (which has much
more tread than the stock primo), I had less problems. The two times I went
down on the TE were on sand and a groove in the road.

I'm familiar with the Manayunk trail. I did the tour de Philadelphia a few
years ago. There is one awful stretch that is gravel ended by cobblestones.
I had a Penninger recumbent trike at the time with Primo Comets. The
cinders/Gravel ended up wearing a hole in the side wall. At the end, it
could not even climb the cobblestones (the wheels just spun). I might add
that that bike ride was one of the hilliest I had ever been on (not the
schukill trail, but the streets which had stop signs at hill bottoms, then
killer hills to climb on the other side of the stop signs.)