Honestly you drew your plans out perfect. Only question I have is, are you going to be using a submersable pump or a plumbed external pump? If I can find pics of my stepdads old 180 gal I'll post them for you. Your illustration nails our old setup almost to a "T" only we came out the side of the sump with piping to the return pump instead of using a submersable pump, but then again this was 10yrs ago. The main differance was reliability and diversity in options and costs.
I'm going to put the rest in caps just because this is the very most important thing when using sumps.
PLEASE PLEASE BEFORE PUTTING ANYTHING IN THE TANK OTHER THAN SUBSTRATE AND DECOR FLIP THE SWITCH TO GET YOUR FULL FILTRATION CIRCULATION GOING THEN KILL THE POWER AND PAY ATTENTION TO THE WATER LEVEL IN THE TANK AND SUMP AT THE SAME TIME BE SURE TO TAKE NOTE OF THE WATER LEVELS AND WHEN YOUR SUMP IS ALMOST FULL CLICK THE POWER BACK ON. NOW ONCE YOU'VE MARKED YOUR TANK LEVEL MIN AND SUMP MAX GO ANOTHER 1" ABOVE THE TANK MIN(WHEN THE SUMP IS ALMOST FULL) AND DRILL A 1/8TH INCH HOLE IN ANY RETURN LINES YOU HAVE. THIS WILL BE YOUR MOST RELIABLE SIPHON BREAK.
I've had people I've known personally that trusted siphon break systems and ended up with half their tank water on the floor.
ONE MORE NOTE TO THAT METHOD OF SIPHON BREAK IS TO CHECK FOR ALGEA GROWTH AS IT WILL CLOG OVER TIME.