  Standard weak measurement with an assistant pointer and single weak
interaction constrains measurement precision and quantity of interaction
parameters, and a compelling characterization of quantum effect featuring
weak-value amplification (WVA) remains elusive. Here, we theoretically and
experimentally demonstrate an enhanced dual-pointer WVA scheme based on
multiple weak interactions and variable spectrum sources. Developing triple
weak interactions, momentum P pointer reaches an optimal time-difference
precision of $3.34 \times {10^{-5}}$ as at 6 nm spectral width, and intensity I
pointer achieves a displacement resolution of 148.8 fm within 400 kHz
linewidth. A quantum effect associated with an anomalous weak value is revealed
by an observable violation of a Leggett-Garg inequality. The I-pointer weak
value is measured to be 1478 using multiple weak interactions and high
signal-to-noise detection, achieving a two-order-of-magnitude WVA enhancement
compared to standard weak measurement. Our work opens up a practical avenue for
minuscule quantumness measurements in challenging environments.
