Thanks for your questions.
it aims to create a new non-inflationary and elastic currency backed by Bitcoin.
Kind of. Let's be precise:
  1. Bitcredit is a currency redeemable 1:1 in bitcoin.
  2. As it is credit money it is elastic, yes. However, it is strictly limited by proof of real value.
it sound like you're making a currency with a fixed exchange rate to Bitcoin.
Yes, the buildup of this elastic bitcredit M1 on top of fixed bitcoin M0 will stabilise the value of bitcoin AND bitcredit, as it is 1:1 to bitcoin.
How is the bitcredit UTXO redeemable for a bitcoin UTXO if it's backed by a "broad basked of goods"?
When buyers pay sellers of real goods (or services) with a bitcoin denominated e-bill, their liability is "backed by the goods" they bought. When these buyers then pay the bill of exchange at maturity in bitcoin on mainchain, this provides the input for bitcredit redemption.
So e-bills are a derivative of bitcredits?
No. commercial e-bills denominated in bitcoin are the raw material from which wildcats (Bitcredit Full Nodes) mint bitcredits.
Hope that clarifies.