I agree on using sufficient Prime (or any other water conditioner) to treat the approximate amount of water added. A bit over is fine, I don't measure but I have a rough approximation of how much I squirt in. No point in wasting money, or in adding more chemicals and TDS [total dissolved solids] than necessary.
That light should be fine for intensity. The watts is rather meaningless, but I know those tubes so I have a fair understanding of their intensity and it will be sufficient.
Dose Flourish Comp the day following the water change. I'm not sure this is that essential, but Seachem did tell me that Prime would cancel out the trace minerals in Flourish, so waiting a day may have some benefit. I used to use Flourish at the water change, now I wait a day, but I can't say I have seen any difference.
On removing the leaves, remove the worst (any covered). But you don't want to remove all the leaves or the plant will suffer. From those photos, I would leave most of it.
By the way, one photo shows an Anubias (it is even flowering)...this plant should not be under direct light as it is notorious for getting brush algae in light. It needs shade, under floating plants is fine, or with an overhanging large sword or something. That would help too.