Sounds like you have the repro slings, you have to heat the opening between the feet with a Bic lighter on the face side moving it rapidly and then reform the opening with your pinky finger.
The repros are narrower and not as deep as the originals and I reformed a few sets for buyers that had the mod before sending them out.
For the wobble check the pin the arm goes on and if it is loose you can swage it tight with a hammer or replace it.
For the too far forward movement stretch the spring out and reinstall.