Yeah setting it up that way should fix it, and help equalize the flow. Swapping that smaller straight pipe in between the 2 totes on the end with a reducer T fitting is probably the best bet if you can still fit one in. You might need another bushing or reducing type adapter in addition to get whatever T fitting you find down closer to 1" or even less to run back to the res. Your options are more limited with plus size fittings like that, so don't expect to find a 3x3x3/4" reducer T for example...
It looks like you have 2-1/2" or bigger main lines which is good though, and should work ok even with all the 90s. Even if the 800gph spec isn't true, even 400GPH should recirculate the whole system many times after so many minutes. Depending on which bulkhead you fix the pump to inside the res with your current config could make a big difference, but ya I would pull from the other side instead of trying to make a complete loop work.
The mag drive pumps are kinda finicky like that.. They seem to work best when fed with a longer length of smaller diameter tubing that is around the same size as the actual port, and installed toward the very end of the line right before the res when possible. The small impellers aren't designed to push or pull all the water at once, and need the smaller incoming line to act like a bottle neck of sorts as it feeds the pump.
The thing is, you really need an inline Y- filter before the pump (whether inline or submersable) to trap any debri from clogging it up when setting up this way. The smaller 3/4 and 1" regular garden irrigation y-filters are too small IMO, and clog up too quick, unless you install 2 or 3 of them side by side with another small manifold. Or, just buy one bigger 2" banjo brand y-filter, with 80 mesh screen for around 50-60 bucks, which is what I reccomend for any RDWC systems. They have way more surface area than thy small ones, and never clog.
