Would multiple Trepanation Blades Stack?
Yes. When the equipped creature attacks, both triggers go on the stack at the same time (in an order of your choice), then are resolved one at a time.

So, for example, I attack with an Invisible Stalker wielding two Trepanation Blades. Both triggers go on the stack. We resolve the first: spell, spell, land; the Stalker gets +3/+0 until end of turn. We resolve the second: spell, land; the Stalker gets +2/+0 until end of turn. Now my Stalker is a 6/1.