To be clear this is *not*, as you say, "starting over". They started with the existing OpenSSL code and worked from their. So they are using the exact same "mature code" and any issue they find are also issues in OpenSSL. Once fixed they are added to LibReSSL and _remain_ in OpenSSL. However, Do not mistake "old code" for "tested code". It was not tested, which was your third point "Bugs are not shallow if the eyeballs are not there." Now that people *are* looking at the code bugs are been found. Case in point the new team brought on board by the Linux Foundation to help fix OpenSSL reported on 5th June 2014: CVE-2014-0224: "a Man-in-the-middle (MITM) attack where the attacker can decrypt and modify traffic from the attacked client and server."

So let's look at what was actually removed in the first week. arstechnica have an interview with Theo de Raadt and he describes exactly what they removed.
https://arstechnica.com/information-technology/2014/04/openssl-code-beyond-repair-claims-creator-of-libressl-fork/
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de Raadt said there were "Thousands of lines of VMS support. Thousands of lines of ancient WIN32 support. Nowadays, Windows has POSIX-like APIs and does not need something special for sockets. Thousands of lines of FIPS support, which downgrade ciphers almost automatically."
...
There were also "thousands of lines of APIs that the OpenSSL group intended to deprecate 12 years or so ago and [are] still left alone."
...
De Raadt told ZDNet that his team has removed 90,000 lines of C code. "Even after all those changes, the codebase is still API compatible," he said. "Our entire ports tree (8,700 applications) continue to compile and work after all these changes."
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So to summarise the facts:
90,000 lines of *unused* or *obsolete* code is removed from the LibReSSL code base.
90,000 lines of *unused* or *obsolete* code remains in the OpenSSL code base.

If the Industry Average is 17.5 errors per 1000 lines of code*, and there are 90,000 lines of code, we can calculate that the OpenSSL code has 1,575 MORE errors than LibReSSL

( 90000 / 1000 ) x ( ( 50 - 15 ) / 2 ) = 1,575 
* "Code Complete" by Steve McConnell. 
Blame Charles in NJ if my math is wrong.