I don't know an easy way to dump the list of patterns/signatures being enforced by the gateway, but you could try giving your custom indicator a unique name, install policy to the gateway, then try to grep for the name of the custom indicator out on the gateway where it has its complied policy cached like this:
grep -i indicatorname $FWDIR/state/local/FW1/*
grep -i indicatorname $FWDIR/state/local/AMW/*
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