To address the issues of unstable electron trajectories, poor radiation collimation, and low high-harmonic energy utilization in nonlinear Thomson scattering, this work investigates the modulation effects of tightly focused, circularly polarized, ultra-intense, ultrashort laser pulses with different pulse durations under a spatially nonuniform magnetic field varying with the transverse coordinate. The normalized Lorentz equations are numerically integrated on the MATLAB platform to obtain the three-dimensional electron dynamics, while the spatial radiation distribution, maximum radiation power angle, and radiation spectra are analyzed by combining the Larmor radiation power formula with the fast Fourier transform (FFT). Results show that the nonuniform magnetic field effectively suppresses the radial divergence of electrons, leading to stabilized trajectories that evolve into columnar helical structures. As the laser pulse duration increases, the radiation angular distribution gradually transitions from a vortex-like pattern to a highly collimated conical shape. When the pulse duration is L=5λ0, both radiation collimation and high-order harmonic energy reach their optimum, with the maximum radiation power angle stabilized at approximately 3.5° and the spectral bandwidth extending to 3000ω0. However, excessively long pulse durations introduce asymmetric distributions that reduce harmonic energy. These findings demonstrate that an appropriate choice of pulse duration, in the presence of a spatially nonuniform magnetic field, can achieve highly collimated and high-energy X-ray radiation modulation, providing theoretical guidance for the optimization of high-harmonic radiation sources.