Thank you, it was rewarding but time consuming.
You should post pictures of how your sump will be placed along with your tank. That provides a better visual for the best runs. The best looking plumbing isn't always the most efficient, but Im ok with that.
I would agree with some of his suggestions. Two return pumps is a good idea for redundancy. Another option would be look into DC pumps where you can control the flow. Good value are the Jebao, although I have not used but many on here like. There are numerous other brands.
I would use a check valve from each pump run to prevent back siphon. I would use loc-lines to each side like he said assuming your tank back is against a wall.
When setting up you want will want to test that when your power is off, your sump will be able to contain the water returning to your sump. In your case, it will be the level of your main siphon drain. This will minimize any chance of your sump overflowing.
