I know a few people who have built these rigs for themselves and it ends up being relatively expensive to build one that works well. Since the goal is to get all of the sediment out of the tank, you need to be able to agitate the tank well. The flow rates that you posted above look quite low to me to be doing this properly. Unfortunately, higher flow pumps like the FASS high flow pumps are extremely expensive (~$500). You do not need a pressure regulator as long as the pump is rated below about 50psi.
Regarding filters, a lot of people use filters made for water systems as the first filter in the line since they flow really well and are cheap. If you need to get your flow rate up and don't want to go with bigger filters than you have posted, running a few in parallel could work.
Ideally, you would have access at the top of your tank so that you could direct the returning fuel stream into different parts of the tank. Since this is often not possible, you can often fish the return hose around in the tank a bit to get it to spray in different directions.
I am not particularly surprised at the cost you quoted. These rigs are expensive to build and the filters are expensive to keep changing. Unless you get bad fuel often, you should not need to do this on a regular basis so it might well be cheaper to just pay the money. The best way to prevent it in the future is to filter your fuel before it goes into the tank and use biocide from time to time so that you catch any algae growth early.