443 is just the central wavelength of B1. It has a bandwidth of 20.
Sentinel-2 - Missions - Resolution and Swath - Sentinel Handbook - Sentinel Online (esa.int)
So, you should consider at least the values from 433 to 453. Probably, it is good to sue also the other wavelengths provided.
The latest SFR table differs from the on you are using:
Sentinel-2 Spectral Response Functions (S2-SRF) - Sentinel Online (esa.int)
The equation for the convolution is given here:
filters - Convolution of spectra to sensor response function? - Signal Processing Stack Exchange