No probs Ed! Happy you found it useful. :)
1. I think that if you are looking for compability with the Peninsula, the main issue is if you're looking at pre-1813 or not, and whether you care about the actual year or not. If you care about making a pre-1813 force, I'd go with Victrix, or Warlord if you don't like building multi-part plastic miniatures. But personally, I fudge things a bit and use all my minis for both Peninsular and 1812, even though some of them have uniforms that were not really in common use until 1813.
2. If I had a larger budget, I'd think about whether to go for metal minis or plastics. There are some really nice metal minis out there that are a tad more expensive. On the other hand, plastics can be convenient due to the lower weight. And yet again, some people prefer heavier minis. Even if I went with plastics, I'd add more metal leader models from various ranges, because they make the entire force look better.
SP2 is not a huge game, so once you have built the core of your force, what you're adding is more options rather than fielding a bigger and bigger army. But with a bigger budget, I'd probably immediately get two boxes of Perry's plastic cavalry. You want at least two Groups (so 16 men plus command) of the same type for them to really work well in SP2, and cavalry just look awesome in any Napoleonic army IMHO.
3 – Our Russian player is working on his own version of a starter guide, but I think it will be a box or two of Perry's plastic Russian infantry, and then a few blisters of skirmishers and/or carabiniers.