What do i need to do to share TB and Lightning files between W7 and Ubuntu 14.04 on a dual boot system?

Question

I recently installed Ubuntu 14.04 alongside W7. Since I'm not comfortable dropping Windows completely yet, I want my W7 Thunderbird and my Ubuntu TB to have access to the same data file holding current messages, so I don't have to get out of one to use TB on the other. I rely on Lightning and also want my reminders to be consistent from either OS. I have a separate NTFS data partition which, I understand, can be used to house the profile directory (though I've not seen that as a solution for Lightning).
In trying to set it up, I've run into questions that I can't find a good answer for -- want sources that address the problem and are recent. I'm pretty patient, and I can stumble through a lot of things (like learningn about partitions). But I'm not a programmer, and this start-stop-sort-through-dozens-of-old-incomplete-and-irrelevant-answers process is frustrating. (Nor do I lift the hood and tune my own car engine.) I also recognize that some things I want to do aren't necessarily common, so they're not at the top of anyone's "tell the world how to do this" list.
1. My profiles directory has 6 *.default files. I assume the current one is the most recent. Do I need the older ones? How did I get them, since I've never knowingly created a new one? I'm the only user of my machine and thus the only user for TB.
2. I saw the following before setting up the dual boot system, so it's likely not related -- but if someone who knows TB well can comment I'll appreciate it: when I view All folders, I see 58(!) folders with names nstmp-##. The contents overlap with normally-named folders, but the sets of messages are not identical. Do these indicate a problem and/or should I change something? Does this have to do with compacting or archiving, neither of which I do? Never saw the need, and never saw an article saying that they're important. I just want to use mail and reminders. And BTW I've been using TB/Lightning for years and am Very happy with them, so I want to keep using them.
3. Is there a way to set up Lightning to hit the same data file(s) on my data partition? Or somewhere? Where are Lightning's files? I remember one source mentioned linking to "storage.sdb", but (1) I can't find the reference again, and (2) links to some of my files don't always work. Broken links aren't Mozilla's problem, but someone might know how to geet around the problem for the sake of Lightning. Also, storage.sdb and calendar* directories exist inside my *.default profile directory -- so why would I need to link anything? Are these not where calendar data is stored? If not, where?
I'd rather understand the reasons behind recommended procedures ("do A because Y is how Lightning/TB works" -- vs "do A, then B, then C...and it will/should(!) work."). But if you can point me to a clear procedure that will get me where I want to go, that will be enough.
Last, the following two URLs looked like they would help but don't -- so you don't need to point me to them again:
http://kb.mozillazine.org/Sharing_a_profile_between_Windows_and_Linux -- this is only 2 years old but:
(1) it only says that "settings" specify file locations, without saying which settings. Stumbling around, I found "Local directories" under Server Settings. For more detail the page refers to an article that's 10 years old. Neither source says which subdirectory under *.default should be the target. The older one references ".../mail", but when I enter that value in Local Directories under Ubuntu, nothing shows up. When I went down one more level to "/Local Folders", the folders appear and the new-message counts seem(!) ok. But I also got a couple "folder missing...will adjust filters" messages. I never got those under Windows. So am I good to go, or am I missing messages?
(2) The above page only says that Lightning is a "potential problem", with no suggestion of a solution or link to a discussion. Searching results in many hits, but I haven't found anything helpful.
http://ubuntuforums.org/showthread.php?t=1624973 -- this looked promising, but the comments are dated 2009-2010, deal with ubuntu 10 and XP, and don't seem to address my problem -- unless I'm not savvy enough to recognize it, which is entirely possible.
Thanks for any insights.

Answer 1

Lightning is a problem for you because it hooks into Thunderbird at a low level and you need a version compiled for the platform Thunderbird is running on. So you can't do the preferred solution, which is to put your whole profile in a shared folder and have both instances of Thunderbird reference the same profile. (Ditto for Enigmail). Lightning may become an integral part of Thunderbird in an upcoming release, at which point this limitation due to Lightning should disappear.
And if you can't use a shared profile, you can't set your Lightning, or your Address Book, to share a common set of files. Put another way, the linkage from Thunderbird to its address book files and calendar data is hard-coded, and not exposed where we can adjust it. :-(
The halfway house is to place your mail stores in a shared place, and use the Local Directory setting in each account's settings to connect to it. They don't need to be in the profile; what's more important in your case is that they are in a folder accessible to both operating systems.
Look in your profile; everything under Mail and ImapMail needs to be moved out to a shared folder. Note the entries in Thunderbird under Local Directory before you do this, and reconstruct those pathnames in Thunderbird, but adjusted to suit their new locations.
(You can see here that you need to make many adjustments, one per account, in each instance of Thunderbird, so it's a high-maintenance solution and this is why we don't recommend it when the alternative, moving the whole profile, is possible.)
I share address books and calendars between Thunderbirds on various computers (and my phone and tablet) by syncing to something in the cloud; Google Contacts and Google Calendar are my choices, using gContactSync and CalDav.
Having made the break myself some years ago, I'd recommend you break away from Windows. ;-)