I hate to rain on your parade. But it looks to me that if you don't already know how to bid these larger jobs correctly and you've been as far off from the others as you mentioned above, that you're probably in over your head here.
That will bite you in the A$$ one day. I've seen dozens of guys go out of business in my time because they got in over their head and didn't really know their production times or didn't adequately consider all the possibilities.
If you're asking these questions and you're that far off, it tells me you're trying to get jobs that are probably a little bigger than you should be messing with. You're trying to take a short-cut to the big time.
The proper way to land big jobs is you get there slowly, and with experience. How do you land a $10K job? By doing a whole lot of $5K-$8K jobs. How do you land a $20K job? By doing a whole lot of $10K-$15K jobs. How do you land a $50K job? By having learned the ropes doing a lot of $20K-$40K jobs. It's the same with these huge jobs you're trying to score. If you want to land a $500K job, then you should probably have a whole bunch of $200K-$400K jobs under your belt first. If you want to land that $890K job, then you should probably have already done a bunch of $300K-$600K jobs.
Had you done this, you wouldn't be asking these questions. You'd know your production times. You'd know the best way to install these. Exactly what kind of things to plan for, etc.
If you do land a big $500K job, the first thing you should say to yourself is, "Uh-oh! What did I forget that all the other bidders didn't?" And then hope whatever it is - is something you can afford to take a hit on.
You're setting yourself up for trouble just guessing like this. Almost every job I take on I know before I even sign the contract just about exactly how long it will take my crew to do it, what surprises might come up, exactly what my expenses will be for the job, etc. How do I always know? Because if I am submitting a bid, you can almost guarantee we've done LOTS of jobs of that scale before. Or at least CLOSE to that scale.