These seem a tad high, could you post the result of a dslreports speedtest (see https://forum.openwrt.org/t/sqm-qos-recommended-settings-for-the-dslreports-speedtest-bufferbloat-testing/2803 for how to best do this for the forum) so we can get an estimate of reasonable shaper bandwidth settings, please?
I believe that on a DOCSIS network this needs to be 64 and not zero.
I would probably recommend cake and layer-cake.qos here as that will allow to configure per-internal-IP-fairness, so no single XBox should be able to spoil the fun for everybody else... But first the speedtests, please 