We propose a multiphoton heralding scheme using an optical parametric amplifier (OPA) that converts a squeezed vacuum into two families of non‑Gaussian states: large‑amplitude squeezed Schrödinger cat states and low‑order parity‑selective Fock superpositions. By injecting m photons into the idler port and detecting n photons at the output, an effective high‑order photon subtraction (k) can be realized in a single OPA device for properly chosen (m, n) pairs, with an effective order k=m+n. The heralded states exhibit strong Wigner negativity and high phase‑space complexity. Remarkably, under photon loss, the complexity remains substantial, even after the negativity vanishes, indicating a loss‑resilient quantum resource. These states exhibit phase-estimation performance that can achieve Heisenberg limit scaling with an enhanced constant factor in certain regimes. Our protocol establishes the OPA as a versatile platform for generating non‑Gaussian states with promising applications in loss‑resilient quantum metrology and fault‑tolerant quantum information processing.