Good ride followed by a good write. Congratulations on your first official 400k though it hardly means anything to you if you had already done 500k before on your own.
Sorry about your loss of the brevet card. All that is excused as you will eventually do longer official rides later ;-)
Hey, about the BITH, I had a few basic sanity test I put across people which can help them decide if they are ready. Sleep is one part which you can manage if you pass this simple test. The test is - run a 50 km or climb Nandi 7 times in a stretch, probably with small breaks of drinks and snacks. If you can manage either of these depending on your preference, with a single cramp or exhaustion, you are ready for BITH. Climbing is what challenges BITH. If you are decently good in it, you can spare time for your naps. It will be a boring test, but it will save you the time from a real ride.
BITH however throws another challenge in the first half due to the afternoon start. The city traffic plus initial need for covering distance without a buffer over the day means that you hardly have the time to nap in the first night. Most riders end up riding all the way till Kalpetta, often chasing the cut off time, without any sleep.
It is also helpful to improve downhill ride as BITH has very long downhills on very good roads. Virajpet to Iritty, Doddabetta to Metupalayam via Kotagiri, Yelagiri are all very good roads and are all fast downhills with very less traffic.
You still have two months time before you decide :-)
I keep promising Chiddu that I will support him to run the BITH every year, but I always end up being not so helpful. We will anyway try to make this even happen every year. In fact, I want to this to evolve as a PBP kind of a ride - it has both beauty and challenge and a perfect loop.