Honestly if your durso is siphoning you will know it. The water level will build up in the overflow then when the siphon establishes it will rapidly draw down until the open end of the pipe is exposed then make a loud sucking noise as the air is pulled in and breaks the siphon. The cycle will then repeat. You know it when you see it, it’s like a toilet emptying with the same suck at the bottom end of the cycle. I stand by my earlier assertion that you just need to slow your pump and remove some water from the sump to bring the water back to normal. I really think you should try this before altering your plumbing too much.