I have been wanting to help answer but it has been very frustrating when SRC has been intermittently inaccessible.
1.What are the dimensions of your DT?
2.Do you think a skimmer is necessary for a macro-algae tank?
If you can afford the space, yes. I traded the skimmer for more space so that I can have a bigger collection of macro-algae in the refugium as 'backup'.
3.Are you currently using any po4 remover like rowaphos etc?
Yes, GAC too. macro-algae does not 100% clean the water. In certain situation, it may even make the water more green or yellow. I do monitor the PO4 to ensure it is still traceable so that the macros are not totally starved.
4. Any other tips
Replicate zones with different flow rate in the tank with the wave maker. Certain macros do have flow requirement, especially the non-green ones. Avoid angelfish, tang if possible.
Hope there are helpful