MPE 7: REMN Internal Dynamics and Field Curvature:The Rotating Electromagnetic Nozzle (REMN) is the primary thrust-generating element of the Griffiths Canon propulsion architecture, appearing in the GNMT megawatt-class drive, the H₂EM propulsion variants, and as the plume-shaping nozzle in the MSH Drive. Previous work established the REMN plume series (ICD simulation suite, SIMs 1–16) and the REMN+ REBCO upgrade architecture. What has not been formally developed is the internal dynamics of the REMN: the structure of the curvature field κ(r,z) within the nozzle volume, the mechanics of rotational confinement, the conditions under which the rotating field provides centrifugal stabilisation against Kelvin-Helmholtz and interchange instabilities, and the physics by which the EM field extends the stable flame attachment zone in combustion-coupled variants. This paper provides that formalisation. Section 2 introduces the REMN internal geometry and the field architecture from coil nodes to throat. Section 3 derives the curvature field equations and maps κ(r,z) and Ω_rot(r,z) across the nozzle volume. Section 4 develops the rotational confinement theory, establishing the Rayleigh criterion for centrifugal stability and the stability parameter Φ_stab = Ω_rot² / (γ_KH · κ) that governs the REMN operating envelope. Section 5 derives the EM-assisted flame extension model, connecting the burning velocity enhancement to E_gate and local electron density. Section 6 presents the internal performance envelope spanning the REMN baseline and REMN+ REBCO regime. Five falsifiable predictions are derived. The framework provides the internal physics foundation that connects DIGSP topology governance (MPE-5), λ-combustion control (MPE-6), and the integration architecture of MPE-10. Keywords: REMN, rotating electromagnetic nozzle, curvature fields, rotational confinement, Rayleigh criterion, Kelvin-Helmholtz stability, EM-assisted flame extension, Karlovitz stretch factor, REBCO, REMN+, Griffiths Canon, plasma nozzle dynamics