#1 I agree with the value of mock drafting. It does help in rounds 1-6 a little because you can get an idea of perceived player value. Draft picks vary league-by-league, but I really think mock drafts help me see what type of players I can expect to see if I get an early, mid, or late round pick for my actual leagues. You start to see draft patterns and get an idea of who you can target in what round. In the late rounds, personal preference definitely takes effect and I start getting very similar benches. I'd also say, your first 2-3 rounds should generally be "safe" picks with very little bust potential and following rounds need to be looking more at upside. Also, since your bench was drafted for upside, do not be afraid to give up on a bottom-of-the-bench player early for someone else off to a hot start. Getting the right free agents after the draft can also lead to championships.
#2 I don't agree with your reasoning behind playing in 2 or more leagues. Always start whoever you think gives you the best chance to win. I'm not going to be splitting the risk and starting two different players if I think one is a better option. What playing in multiple leagues does get you is the chance to increase your experience faster by evaluating multiple teams, lineups, and free agents every week. If I'm in multiple leagues, I'm playing like I can win all of them instead of splitting risk and trying to increase chances to win at least one.
#3 I agree with avoiding injury risks early. I wish I hadn't taken Spiller in one league just because he fell into the 2nd round - Graham and Forte were both available and were players I was more comfortable with but I chased upside instead of making the safe pick in round 2. However, the later in a draft it gets, the more likely I'm willing to draft another injury risk. To win a championship, you need to avoid busts early and get a few steals late. If a late-round injury risk has a lot of potential, I've got no problem grabbing a few. You can always pay attention to the waiver wire and make changes if late-round picks don't work out.
#4 The main point I see about your trade example is try to get the best player in a trade. Basically, any sort of 2-for-1 deal where you trade depth for talent is a good move, but it can be hard to pull off. The Moreno/Amendola offer would have been better if you needed a potential RB2 and had a weak bench. The Fitz offer is better if you're off to a good start and have a strong bench. Either way you sell high on Bell. He's a backup, low-end RB3 until Bush gets hurt. Even if he is behind an injury risk, I'd almost always rather have the player that can help me now (Moreno or Fitz).
#5 Since you mentioned matchups in #4: Never sit your studs based on matchups. Picks from rounds 1-4 should almost always be starting. I think matchups are most beneficial if you stream defenses week-to-week. For example, almost any defense playing against Jacksonville is a good call right now.