All I can give is a bit of advice here of how I run my sub-ohm rebuildables.
1) Ohms I'm generally in the 0.5 to 0.75ohm range, I like more flavor with a decent amount of vapor which equates to more wire to wick contact with thinner wire than most use, generally my sub-ohm RTA's I use 26awg, want to bump my resistance higher I use 28awg wire for my builds then. Safety wise on a regulated mod like the 213, you just have to stay above it's minimum resistance it will fire and you are actually pretty fine, the chipset handles the rest of the variables, on a mech/unregulated even with 30amp CDR batteries, dual parallel mech lowest build is 0.14ohm, dual battery series about 0.55 to 0.6ohms lowest, single battery about 0.25ohms lowest.
2)Watts and Volts go hand in hand, (Voltage Squared / Resistance (ohms)=watts, so I run about 30 to 40 watts on these, which equate between 3.7 to 4.4volts depending on the build.
3) Temp is an entirely different beast due to the different wire materials, and I run these by liquid flavor dependent variables (some liquids I like warm like my rich RY4 tobacco flavors or coffee flavors to cooler with a fruity flavor). Nickel Ni200 setups I am in the 0.12 to 0.18ohm range on a dripper, watts about 40 to 50watts, temperatures 380F to 490F, Titanium Ti1 setups I'm in the 0.25 to 0.35ohm range, same watts and same temps. Stainless steel coils I'm in the 0.4ohm range, 50 to 60watts in the 400 to 520F temp ranges.
4) Amps - this I can give a little more focused information, this is electricity, so "Ohm's Law" applies, volts, watts, resistance, and amps all go hand in hand. On a mechanical unregulated mod where the only voltage throttle is the charge level of the battery, to figure out how safe our builds are we use this formula (voltage (fresh charge battery is 4.2v where the highest amp draw will be so we use that figure)/resistance (your ohms)=amps [exampes - 4.2v / 1ohm=4.2amps, 4.2v/0.5ohms=8.4amps, 4.2v/0.25ohms=16.8amps]
With a regulated mod, we still use "Ohm's Law" but a different formula of (Watts/Lowest Battery Voltage/Mod Effieciency=Amps) [examples - single battery mod 60watts maximum output, most mod shutoff at about 3.2v, so we get 60watts/3.2v=18.75/90% Mod effieciency=20.83333_ Amps, being that you are using dual battery series mod which the batteries have the same mah and amp limit so those figures stay the same, yet voltage is doubled, so example here using your figures above we get 35watts/6.4v (3.2v per battery X2)=5.46875/90%=6.076388888888889 or 6.0764amps rounded up]
5) Batteries - buy them from reputable and authorized distributors (Illumn.com, IMRBatteries.com, Liionwholesale.com, Orbtronic.com, RTDVapor.com if in the States are the most suggested resellers), second there are mainly 3 brands suggested, LG, Samsung, Sony want model numbers and excellent independent testing spec sheets check out
@Mooch he's our resident battery tester and there is also torchythebatteryboy over at the UKVapers forum, but for your vaping style, there are these 4 models that will work excellent for you, good run time and good CDR, Samsung 30Q (3000mah 20amps), LG HG2 (3000mah 20amps), AW IMR 3000mah 20amps, Sony VTC6 (3000mah, 15amp factory cdr spec like the 30Q is but Mooch up the safe CDR to about 19amps almost 20amps)
