Corey did a nice job answering your questions, but I thought I would add a few more tips.
1. The Venator isn't meant to be a front line warship, it's your carrier, and it should be used as such, keep it away from the NR warships if you can, since its main weapon is its fighters and it's rather fragile.
2. I would personally recommend VSD1s instead of VSD2s, because they are much better at handling starfighters, and the NR loves starfighters, additionally, if I remember correctly the VSD1 has better burst damage, especially against hulls.
3. Be ready to kill lots of Viscounts, from what I remember the AI gets a ton of income, and holds more than a few capital shipyards, I recommend a combination of carriers and cruisers/frigates (think VSDs, dreadnaughts, etc.). Make sure you don't deploy your whole fleet at once, upon making contact drop your cruisers and frigates into it's blindspot and use micro to keep them and your bombers there, hopefully the supporting fleet will be manageable, and you can mop up after dealing with the Viscount. Might also want to use an Interdictor to prevent it from fleeing. Otherwise, the best counter is another SSD and it's supporting fleet, using similar tactics.
Hopefully some of this might help you.