The microscopic interplay between superconductivity (SC) and ferromagnetism (FM) in EuFe(As_1-xP_x)₂ remains elusive, as the overwhelming Eu²⁺ ferromagnetic background masks SC signatures in conventional measurements, obscuring their coupled phase boundaries. We overcome this by utilizing an ac composite magnetoelectric technique, exploiting the opposite magnetostrictive signals of the SC and FM phases to successfully disentangle the H–T phase diagrams for samples with T_c<T_FM and T_c>T_FM. We identify two distinct SC suppression mechanisms. For T_c<T_FM, SC is disrupted by static magnetic domains via the breakdown of Jaccarino-Peter compensation and vortex-antivortex nucleation at domain walls. Conversely, for T_c>T_FM, strong pair-breaking from dynamic short-range spin correlations near the triple point suppresses the upper critical field. These findings reveal how static magnetic disorder and dynamic spin fluctuations distinctly reshape superconducting pairing in complex quantum materials.