How to choose a suitable cutoff

Hello lammps users
I run ReaxFF simulation with lammps for C3F3H2Cl thermal decomposition,but the output file species.out shows that the system contains C21CI8F23H14 as temperature was not controled。

My question is

  1. Whether the clustering of molecules is caused by the unreasonable setting of cutoff? cutoff is the default value of 0.3

  2. According to what adjustment cutoff and set different cutoff between different atomic types

  3. Can it be improved by expanding the simulated system size (reducing the density of the simulated system)?
    HCFO1233ydZ.species.out (3.4 MB)
    Pyrolysis.lammps (2.8 KB)
    Look forward to receiving your advice!