A few questions

freshwater inverts can handle copper better then SW, but neither should be expossed to it. RO water will remove most material in water. Copper is a hard one to work around but wont normaly promote a problem as long as your using RO water.

Sand is a must. Sand has certain propertys that gravel can not replicate. Gravel will trap debris and cause them to breakdown in the water column causing catastrophic nirtate problems.

crushed coral and gravel can be used but they require more maintanence. and no, SW organisms in general do very poorly when exposed to copper. best way to not get it into your tank is to use RO or RO/DI water because the filter will pull out the copper and give you very pure water.

Sounds like a ton more research is necessary, before you even consider starting a SW tank. Start here: http://www.marinedepot.com/md_StartAquarium.html

the contientous marine aquarist and the new marine aquarium.... you need to invest in those books...

you can use tap water if you're sure there isn't any copper in it and nitrate and phosphates are low enough but you will be more likely to have nutrient problems because tap water usually isn't anywhere near as pure as RO water. and you don't have to use sand, if you use CC or gravel you just have to make sure you vacuum it very frequently and thoroughly like in a FW tank. you could do cardinals, clowns and the hawkfish in the 35g but the dwarf lion is going to get too big and messy for a tank that small, esp. in the hands of a beginner. you can use live rock to see base rock but you have to make sure the base rock your using is safe for saltwater, some of the rocks like the lava rock will release phosphates that will encourage a ton of algae problems, the best base rock to use is dried live rock. if you want to use sand then live sand isn't really needed, you can use regular dry sand and the bacteria and micro-life will colonize it just like the base rock.

is there a store around you that sells RO water. If so i would go that route. If not, then i might suggest getting your own RO unit. They will come in handy when you increase the size of your tank anyways, so wouldnt be totaly unnecessary.