@Bigellow - While I don't work for Lockitron, I can help answer some of these.
Backer Number is the same thing as Place In Line. From here on out it may be best to stick to Place In Line as that's what the Order Dashboard uses.
Amount of units ordered has no bearing on Place In Line, so PIL could essentially be considered an "Order" number. The numbers themselves are static, so they do not change at any point, even if someone else in-between has cancelled their order.
@cameron might have to fill in the blanks here, but this is essentially what happens next.
The (very) Simplified Lockitron Queue Process:
Lockitron assembly is set to complete "x" units
Lockitron HQ starts confirming orders and if an order isn't paid, starts the charge process
Lockitron assembly completes batch of units (this happens at the same time as step 2)
Assembly sends them over to the logistics provider/warehouse
Logistics gets up to date information from Lockitron HQ confirming which orders are still valid and paid for
Logistics packs, labels, and ships units out
The Queue process that is mentioned here and in the e-mails is essentially steps 1 and 2, although to be clear, I assume assembly is running as continuously as possible to keep unit stock ready to go. This is why keeping order information up to date is important, so Lockitron doesn't build more than is needed. There's also a quality control/check step in there, probably between 3 and 4.
When a unit is finished going through the queue, then it ships, and you receive a tracking number from Lockitron/USPS pretty quickly after that.
There was a delay as explained by @pmg earlier in this thread, but that delay is gone. Because a lot of manufacturing is shared (as mentioned in the same post), there may still be production slow downs, but the Lockitron team are probably as anxious as anyone else to move more units through production as quickly as possible. To re-quote Dory from Finding Nemo, "Just keep shipping."
As far as support e-mails go, well, you're getting information directly from the team. @david, @pmg, and @cameron respond to them directly, so you know as much as they know. They want to get your unit to you as quickly as they can.
For time frame and delivery, hopefully today's update will shed more clarity on that.
If you don't mind me asking, what's your place in line? If you placed your order in Feb 2013, I estimate you to be in the 17,000 - 19,000 range.