Topic: Deck and Cockpit drainage
You should "t" your electric bilge pump into your manual bilge pump hose, right near where it exits the boat. And yes, this exit should be above the waterline, as if it isn't, water will just be able to run back in.
Your deck-side drains sound really strange! And yes, dangerous! I think you should have what the later boats have: a open space about three inches (or so) square, right under the toe-rail at deck level -called a "scupper". I can take a picture of mine - it's where you see the water running out the side when someone is sailing on along close-hauled (boat over on its side!)
And yes, all through hulls near waterline, and especially below waterline should always have seacocks...you will at some point need to close them...and mostly just for maintenance...to replace a hose you need to close off the hole! Again, I can send you pics of mine.
And always double hose clamp everything below the waterline.