Sounds like you need to address the broken pipe first, if you want the water level to rise, correct? So maybe that is your first action item.
And if it broke where you see it then it will likely break again beneath the water's surface to I would recommend having it fixed all the way. You mentioned a siphon system, so you may then consider capping that standpipe off after filling it in.
Depending where in Georgia you are you will always have turtles entering your pond. Our pond is pretty remote, and it is surrounded on 3 sides by steep "hills", but I still spot new turtles occasionally. We've got 2 snappers I know well, but I do wonder where the new sliders come from. Turtles are pretty slow on land. Yet each year there are 1 or 2 sliders that appear. And that amazes me because the land all around our pond doesn't appear to be turtle friendly land. lol
What do you want from your pond? What are your goals? Do you want to make it natural and have water plants and wildlife? Fishing? Swimming?