TMS320F28375S: SN29500 FIT calculations vs TI FIT numbers

I have a very similar question to this post:

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000-microcontrollers---internal/f/c2000-microcontrollers---internal-forum/416020/tms320f28334-fit-rate?tisearch=e2e-sitesearch&keymatch=sn29500#

In order to come up with electronic component FIT to use for safety function calculations, my customer has been using vendor FIT data for ICs. The customer has recently requested to start using a more conservative approach using prediction #s per SN29500.

 Thus the following questions:

1. Is the IC construction data needed for SN29500-2 FIT calculation generally available for ICs? (ie. number of gates and/or number of Transistors, etc.) How hard is it to get this information?
2. Would it be possible to explain SN29500 based calculation of FIT for the following parts below:
   1. TMS320F28375SZWTT
   2. F280049PZS
   3. TMS320F28335PGFA 
3. How do the SN29500 based  FIT numbers compare to the FIT numbers produce via TI reliability testing and also reported on TI website?
4. Do the SN29500 based FIT numbers make any sense for the real world?
5. What is TI’s opinion on using the SN29500-2 for FIT vs actual TI reliability test data for evaluation of safety function calculations?

 Thank you!