Don't do these all at once... you may fix it quickly with the first suggestion.

Go back to the tailwheel, and sprng load it to stay centered, but allow some pressure to make it turn a bit. The turning rubber wheel will give better control of taxi on pavement than any skid.

Verify the wheels have no VISIBLE toe angle, and when measured carefully, absolutely no toe-out allowed. 1 to 3 deg toe-in is allowable. More is excessive.

Next... try shifting the axles to be directly under the LE of the wing, to 1/2 wheel dia forward of that location.

Verify CG at or forward of 30% mean chord. (straight wing it would be 30% of root chord)

CG and wheel location can play havoc with a taildragger's ground performance.

If that don't fix it... send digital pics. There'll be a visible problem.