I think you'll like the TLF Phosban reactors. I've run them for a year or so on our previous tanks. You may be able to combine carbon and GFO in a single reactor if you get some extra foam filter separators to keep them apart.
I just setup a second Phosban 150 on our sump, so we have one running carbon and one running GFO. I put them in series and I'm driving them with an MJ1200. I like your manifold off the return, but I was worried a manifold would make the return flow less consistent and require more frequent tuning of my herbie drain.
Tank and sump are looking good. The anthias look great.