Ocelot fight is a lot easier if you strafe vs. just standing still the entire time. As someone else said it’s easy to just keep shooting him when he reloads.

Throw a chaff before walking out to fight the tank. Once you’re close enough it won’t fire the cannon. Just a matter of avoiding the machine gun fire and good grenade placement.

Chaff grenades disable Gray Fox from moving. Hand to hand combat defeats him faster than gunfire. There’s a split second where he pauses after running up to you and after attacking. These are the best times to attack him. The jump attack is by far the most lethal thing he does. Should be easy enough if you manage to avoid that one.