1: Fewer hands will increase variance, not decrease it. If you are making mistakes it will be amplified by the larger handset. If you are losing money online it is not because of the increased variance, its because you are a losing player.
2: If you are playing 3-4,000 hands an hour online, maybe you should reduce the number of hands you play. This is NOT to reduce variance, but rather to give you more time be thoughtful in your play. If you play your A game when you do 1 or 2 tables, but a B game when you play 5 or 6, don't play 5 or 6 tables. While you will be getting fewer hands, you will be getting better results because you are playing a better game of poker. You may be a winning player when you do 2 tables and a losing player when you do 6. This isn't because of variance, but rather because you are a better player when you can focus more on what is happening.
3: Live poker is a pretty different animal. You give out more information, but you are also receiving more information and at the same time forced to play only 1 hand at a time. This means you will be more attentive to detail. What you may be finding is that the action at a single live game is much easier to read and stay focused on than an online table is. That could account for being a better live player than at online.