G-Force

+1 with temp at 28. You can drop it down to 27 with a big water change as well to help simulate their natural environment.

Cave size shouldn't be an issue at all, they love a tight fit. But definitely reduce the number of caves. I like having the cave close to other driftwood so that the females will hang around naturally.

I've never had an issue with lighting effecting breeding but that's just me. Plenty of people online on both sides of the lighting argument. 

You can do a planted tank very cheaply or very expensive. How much you put into it will affect how well/fast the plants grow but it is possible to grow *most* plants with just the basics

Substrate can simply be a fine-ish gravel or you could go all out with something like the ADA substrate (http://www.adaaust.c...soil_series.htm). Can also supplement the main substrate with additional bottom layers but I'm not very experienced in that area.

Plants need three things, light, nutrients and Co2. Which ever off these three is the lowest is going to be your growth bottleneck. if you're not using heavy ferts and/or high lightning then you dont need Co2. If you want to have a little bit of a boost you can go the DIY Co2 approach using yeast/sugar (plenty of guides around for this).

Ultimately it depends on what you want out of your planted tank and specifically what types of plants you're looking to grow.

 

One trick I've seen is throw in half a teaspoon of vegemite. apparently it helps the yeast last longer by providing it with a yeast based food