Treadling and suddenly finding going backwards is due to your feet position and lack of rhythm. When the machine gets really free from cleaning and oiling it will reduce this. But you have to develop a rhythm while treadling and that means a smooth rocking motion past the top and bottom dead center of the pitman arm to keep the wheel turning. It's harder to do going slow than fast, but you'll get there.
What I did on my treadles was make an index mark on the stitch length knob with a Sharpie, then turn it all the way in and sew a length. Mark the fabric. Then turn it 1/2 turn out, sew a length and mark it. And so on till it quit feeding the fabric.
Then I used a magnifying glass and counted the stitches and marked that on the fabric with a Sharpie. It's not precise and it's a pain in the butt, however it does work.
Joe