Ah, your big bro (I'm assuming big) influence is noticeable. If you found the rocks locally like that there is a very good chance they are basalt, that's mainly what we have here in Jersey, just not lying around like that in my area.
A 4bulb t5ho is a lot of light, even at this great depth. Check out
THIS thread for a some solid lighting info. High light is fine IF you intend to go into daily dosing of ferts and pressurized CO2 (high tech). My view on it is, if you don't see any lack of light deficiencies (weak plants, small leaves, long stringy looking plants that seem to get denser as they get closer to the light) then leave a good thing alone.
IF this was my tank I would probably go with 2 - 2 bulb home depot T8 fixtures for low/medium light (low at the bottom, medium in the middle of the tank) that covers the back to front spread nicely. At this light level you can still add daily ferts and CO2 to increase plant growth and health too.
Glad to hear you are planning to paint the overflow.
I agree! Not enough young people in the hobby these days! At clubs and conventions I am hard pressed to find people even of my age, younger? Forget about it! And I'm no youngin, I am 33! It is better now (that I'm older) but 9 years ago when I first got into this hobby...a 24 yr old FEMALE at a club meeting was like seeing a unicorn! lol
With someone to guide and inspire you (your bro) I think you will have no problem delivering those "big things". Boy, I'm jealous of having a fish buddy! Everyone I know hates everything to do with fish now that I've drowned them in it! hehe