1 - How much is recent form helping the Galaxy confidence?
I've been hard at work in my laboratory working on a way to measure confidence, and last night my elves had a major breakthrough. The Confitron will not only measure a team's con level, but it also can be yours for just three easy payments of $19.99! The Confitron currently has the LA Galaxy at 21 cons, and gives a pre-recent-form reading of 15 cons. Thus the answer to your question is that LA's recent form has helped them to the tune of 6 cons.
So how has this form led to a con increase? Well the speed which the LA Galaxy displayed on the right side against Real Salt Lake, exploiting RSL's tendency to play narrow, certainly lends them the confidence to believe they can be a wide playing team. Jaime Penedo having a shutout for the entire series certainly lends him the confidence to believe he is one of MLS' top goalkeepers.
If those two areas of the club can just believe in themselves, and with a little magic, this is a team that can con their way to a fifth MLS Cup.
2 - Playing both games with Keane and Omar is a pretty significant shift from the Shield clinching series. How much difference does that make for LA?
It makes at least 7 difference, according to the Confitron. With Omar Gonzalez out, Leonardo had to step into his role with A.J. DeLaGarza cleaning up behind him. Seattle was able to exploit Leonardo's squishy brain liability with the smart play of experience and got to celebrate a well deserved Supporters' Shield as a result.
Without Robbie Keane, LA's attack lacked the person who Landon Donovan counts on to help create. Gyasi Zardes has become a good follower but not a great chance creator. Even at not 100%, Keane was able to free up Donovan so much against RSL that someone everyone knows should be marked was able to break out for a hat trick.
So if we're quantifying, Keane and Omar being healthy and in the lineup is responsible for the current form and thus is more responsible for overall goodness than the form itself. Those guys lifted everyone around them against RSL.
3 - Is Seattle's recent defensive trend something that the Galaxy should worry about?
I tell ya, watching FC Dallas trying to score in Seattle was maddening. Maddening I tell ya! Not because Dallas played all that great and Seattle bottled them up, but because Dallas played poorly. The ball kept spraying around everywhere and it felt like Dallas was doing a lot to create opportunities. My eyes saw Dallas trying really hard, and you could feel the tension. Yet they were clearly outmatched in the series.
I don't think LA will put one in nine shots on target, so I don't think specific Seattle performances are that much to worry about.
4 - With at least 600 fans (most traveling, but some displaced Sounders) will the atmosphere take a bit of a hit, or will that amp the whole crowd up?
27,000 - 600 = 26,400
I know Sounder fans are used to much bigger crowds, really no one in MLS can touch the fan participation in Seattle. Mazel for that. However, I think LA will find some way to manage overcoming the 600 fans Seattle is bringing. Fans who have traveled to the StubHub! Center before know that LA doesn't put the away fans up in an upper deck corner, they get a whole section down in the bowl with the Angel City Brigade just a few sections away behind the goal. When away fans are active, ACB tends to take it as a challenge. It really lifts the atmosphere in the whole place.