Hi Grego, welcome to The Planted Tank!
I have one coralife lamp with two 65w 50/50 bulbs.
I would highly suggest to switch those bulbs to something in the 6700-10000K range. 50/50 bulbs are for marine setup, and less effective in freshwater planted tanks. Keeping the 50/50 will result in not enough light to grow plants.
I purchased and placed in the substrate 3 Large (20 inches tall) amazon swords, 3 16 inches crypts (can't remember name but starts with C), 2 onions, 5 giant val, 3 anubias barteri?, and a patch of java fern on some driftwood.
I recommend to add some fast growers in the beginning. That will help keeping any algae explosions down. Things like Wisteria, Ambulia, Ceratopteris, Rotalas, etc, fast growing stem plants.
The tank has been running for 4 days now. I do not want to add Co2. Here are the questions: Should I add some rummy nose tetras now or wait? Should I add some Sterbai Cory's now or wait? If I am not adding fish how will I get the ammonia in there for the cycle? I have read conflicting info on planted tanks and cycling so I want to be sure I am not wasting my time but I also doon't want to hurt any fish.
Don't worry about adding ammonia. If your plants grow (after you changed out the bulbs) they will gladly uptake any ammonium/nitrite before it will hurt your fish. With a 120 gal water volume, adding a few Tetras and Corys will not add a big bioload where you would have to worry about cycles. Just add fish slowly, waiting a week or so before you add the next batch, this will give your filter and surfaces time to be populated with beneficial bacteria.
Is my light sufficient or should I get to the 1.5 WPG that many suggest? I am running the light for 10 hours - good?
If you swap out your bulbs as suggested, you should be able to grow the most undemanding plants. The ones you mentioned should mostly do okay. The advantage is that you wouldn't have to worry about adding fertilizer incl CO2. But don't expect lush plant growth and lawn-like ground cover!
Should I add some undergravel fert sticks even though I have the flourite? How will I know I need to add ferts to the water column?
I would wait a little longer, see how you plants grow in 3 or 4 weeks (after the bulb change). Once you see new growth show pale yellow or white colors, it is time to add some fert sticks to the roots. With just over a watt/gal, you don't have to worry about water column ferts for a while. I'd add small amounts of Flourish or another micro mix to make sure you are covered there. Watch your plants for signs of nutrient deficiencies.
Also what would be some good low growing plants plants for this setup ( I already have the taller plants but didn't get any smaller ones).
Sorry... but with the light you are using there won't be much choice there. Look for some smaller crypts, they can handle low light. I like to use Wisteria, keeping it as a low light lawn (lll) by pruning it regularly, works alright. Try Dwarf Sagittaria maybe.