dont forget str cape

Can confirm 39 for highest PvM melee hit currently. As you pointed out the player can hit extra hard against demons while wielding the demonslayer's ring.
And the highest PvP melee hit currently stands at 37 as indicated with your avatar.
Both these highest hits can actually be much higher if magic, ranged, or poison damage is inflicted at the same time, but then we're dealing with multiple avenues of damage.
And the highest MvP hit is obviously dragonfire, which can hit in well into the 60s.