It’s actually a really open debate on when to add corals,
Corals don’t actually require a cycled tank so provided the essential elements were stable, you could in theory add them.
Typically new tanks and especially those of new reefers aren’t stable or are certainly more prone to swings due to mistakes (like not heating the water).
If a second heater isn’t an option, then perhaps more frequent smaller water changes would suit (it would actually provide better stability in the long run).
As for the powerhead / wave maker (Nero 3)
Having it on will help kick up detritus and clean the tank, random flow is ideal yes, and I’d personally have it placed on a side opposing the outflow nozzle (this will create further random flow as the two opposing streams of water meet).
I appreciate that aesthetically it looks nicer camouflaged against the black background, so that’s your choice.
I think adding snails now is a great option, 1 conch will sort the sandbed and 1-2 astrea snails will tidy up everything else. (Don’t bother with trochus snails which are commonly available in the hobby, they’re not that great. They often jam your powerhead or like to sit within the fan so you are woken by the rattling noise it makes whilst striking their shells. You will also be horrified when it comes to spawning and they cloud your tank like milk. Seriously, it’s incredible how one small snail can fill a tank with a white cloud)
If not already. Try out PE mysis for the clownfish as part of their varied diet, IMO they’re the best frozen mysis on the market.
Some selcon vitamin is also great for soaking food in and getting the best out of fish.
Sorry for the lengthy post; all these new reef tanks are really making me miss keeping one.