1. Not sure the Zalman fans have been tested on a radiator but if you are confident, it is your build.

2. I cannot get your link to the bracket to work but generally when manufacturers talk about fan spacing, 15 mm is standard. That means it is 15 mm between the holes so the fans will line up next to each other. Some older radiator have 20 mm spacing.

3. Set up your loop so the pump is always filled, i.e. res > pump. After that, avoid kinks and maximize airflow.

4. Loop order won't matter from a thermal/cooling standpoint since water temps are within 2?C in a simple loop.

5. If you want to keep your D5/bay res, and you want pump redundancy, just stick another D5 after the D5 in your reservoir. I use two D5's in an EK dual top (back before the 35x came out). Here is a link to multi-pumps setups.

Happy to help. Good luck.