1) No but my cousin has one and ive been building with him.
2) im using an Efest 2500 35A battery.
3)I got 4 red Efest 2000 batteries, then found out they are crap, so i ordered 4 Efest 2500 35A batteries.
You still need any ohm reader. Things change as you vape and rewick your coils.
The battery you have is actually rated 20A not 35A as printed on the wrapper. 20A is the CDR (continuous discharge rating) and 35A is the pulse discharge rating. Its a good battery, but not a 35A battery. The CDR (not pulse) is what you need to be looking for.
Now as far as batteries for your 150 watt mod. If you are going to stay below 100w than a pair of 20w batteries is fine. However if you are going to be vaping 100+watts you need a pair of 30A batteries. Sigelei actually recommends 30A batteries.
You also need to marry your batteries for life. Use them together, charge them together, don't separate them.
Here's a couple of blogs you should read by Baditude (one of our battery/safety experts).
Purple Efest Batteries not as Advertised
* A cautionary blog that reveals that the purple Efest batteries may not have the specifications advertised. Also includes a commentary on "continuous discharge ratings" vs "pulse discharge ratings" of battery specs.
Battery Basics for Mods: IMR or Protected ICR?
* Another essential read to understand which batteries are safe to use in mechanical and regulated mods. Includes a frequently updated list of recommended safe-chemistry, high-drain batteries with their specifications.