Define your rule as a function:
ruleDerF = ( # /. Module[{x}, Derivative[n_][f][var_] :> (D[x f[x], {x, n - 1}] /. x -> var) ]) &;& f''[x] // ruleDerF f[x] + x Derivative[1][f][x]
FixedPoint[ruleDerF, f''[x]] f[x] + x^2 f[x]
FixedPoint[ruleDerF, f''[1]] 2 f[1]
(havent tested heavily)