The next steps

Ok guys. This is going to be a long read but I'm going to ask a few questions so hopefully you can all help. Ive currently got a 120 litre tank all in one. Protein skimmer, filter and heater. Live rock and live sand.

1) ammonia 0, nitrites 0, nitrates are at 10ppm and pH is at 8. I haven't gotten fish yet, going to wait a week to make sure readings are fine. The question is what test kit next????? As I know I need to start testing for phosphate, calcium etc.....

2) experiencing a bit of green algae across all the glass of my tank. Any suggestions on how to get rid????? I know water changes help so I've been doing a 20% water change weekly after scrubbing the glass. Anything else to help

3) my devils finger has kind of shriveled up. It did look all open and awesome but now just looks like a bald tree. I'm currently feeding every 3 days with reef snow from nt labs.

4) flow.......... What's right for the tank? I'm currently running 2 the jebao sw4 any one with these power heads/wave makers got any suggestions on where to put them and what settings?????

Sorry for the massive post just rather do it one lump than separate posts.

Thanks for all your guidance