make a note of date of this new information you have been given - this is valid reason to change what ahs been going on.
tho of course is hearsay and exW's word - unless she reported/has evidence?
but given you ahve direct expereince of his violence you cant give him benefit of doubt for your child's sake.
you could also call SS for advice and state your concerns pointing out that you have stopped contact to protect your child.
let him then pursue contact thru courts so that you can get the concerns out and ask foronly supervised contact til he gives reports on drug tests etc