just be careful of some unofficial stuff especially if you do not know the guy at all. Some people out there will trick you in order to get you money or labor. They like to think of elaborate stories to draw onto a person's morality and elicit help from them.
I hope you are not in such a situation. Make sure he does start paying you at some point in the future (when his situation straightens out.)
I have to say that i am no fan of flourite in general. i know it has plenty of iron and other nice things, but it can't even be compared to organic soil. the only upside is that its lasts basically forever while the benefits of organic soil go away after a few years.
Its fine to leave puddles i think. like you said it will evaporate.
just try to make a plastic wrap cover out of a couple of sheets taped together. i see you tried.
Mist the plants every day. maybe that will help?
About the flora - pick you favorites, make sketches of what it will look like, what you want it to look like and plant accordingly.
PS: i forgot to mention - I have flourite in my 40 gallon community. have been using it for 3 years now i think. if you check my thread on the 40gal you can see that it can support plants. (all those planted pics are with flourite). I just do now like its performance compared with stuff like organic soil and aquasoil.