If you are correct and your phone was indeed one that came with a Jellybean ROM then that could explain the problems you have been having.
First, you flashed the matrix kernel (which is 3.0.8 and JB is 3.4 kernel). That would cause issues for sure.
About getting a download link for the ROM from Textnow, if it is 4.1.2 JB we desperately need that ROM! Even if you get the other phone and it does have the JB ROM, the Force 4G community has been waiting for this for sooo long for this and you could seriously contribute to helping us get it going!
About making a full backup, I don't know of any method that won't require root, but there is an app in the play store called "Online Nandroid Backup." This app can be used to create a cwm style backup while the system is booted and without installing cwm.
Not only that, but Online Nandroid Backup backs up partitions not normally covered by running backup from within cwm, such as /modem on this device (the radio firmware), and on the htc evo 4g /wimax, etc.
I believe that it's a strong possibility that the reason why we can't get the Sprint JB ROM to work with the 3.4 kernel may be an update on /modem or somewhere else that is not there in what we currently have to work with (an incomplete dump).
If I am correct about that part, then when you flashed to a lower Ice Cream Sandwich firmware (DSF, Boost Stock Rooted, etc.) you would probably see the types of issues that you are having bc a normal custom ROM for the Force won't flash /modem at all so you will still be using the correct parts for the newer 3.4 kernel and that wouldn't jive with the 3.0.8 kernel in those other ROMs.
You may still have the key we need to fix JB on the Force, even though you have flashed lower firmware, it's possible that whatever we need to fix the 3.4 kernel Sprint JB ROM is still on your phone!
Could you possibly run a full backup of your phone with online nandroid backup and then share it to us via something free and easy like dropbox?
As I said, it's possible that the missing piece is there and can be added to the current JB ROM we are working with.
Definitely it would be most awesome of you if you get the other phone and can share a basically untouched firmware with us, even better if they give you a download link or otherwise send you a copy of the ROM.
I WOULD LOVE TO GET MY HANDS ON A VIRGIN ZIP OF THE JB ROM bc that would definitely contain any hardware firmware updates for individual pieces of the phone. I am reading through the updater script of the ZTE Boost firmware available on the site and can see the syntax for how the different firmwares are unpacked individually and where they are placed.
Speaking of the stock ZTE Boost firmware, it is available here
http://www.zteusa.com/media/wysiwyg/boost-force/update.zip
Warning!! Unlike most custom ROMs, the ZTE firmware I linked above will overwrite /modem and probably some other locations that we will not want overwritten if we were going to try and use your current setup to try to reconstruct the missing pieces for the 3.4 kernel included in the Sprint JB ROM. If however, you wanted to try and go down to ICS 4.0.4 (Say to use DSF or whatever) and see if you can get it working with textnow then you should flash that update.zip via CWM.
If you did have a newer firmware, flashing the rom linked above should reflash it with the older modem/wifi/bluetooth firmware versions and allow it to work with the 3.0.8 kernel. Dunno if it will update profile for textnow, and it will have boost bloatware instead of textnow bloatware. Also, you may need to change some settings for MMS, 4g, not sure what.
How long before you are expecting the other phone to arrive? Did textnow actually say that they would provide you an installable ROM? That would probably be even better.
Cheers and thanks for renewing my hope for a fully functional JB ROM!
-SB