Thanks for your help drgeoff! Here's what I found...
1. Caller ID is showing up in history.
2. Regarding the InboundCallRoute field, they're both very different...
The field for line SP1 (the line that works) says {>(XXXX):ph} where XXXX is my obfuscated AuthUserName.
The field for line SP3 (rings, but no caller id) says {(<1:>@@.):ph2},{ph2}
I tried changing SP3 to {>(XXXX):ph2} where XXXX is my AuthUserName for that line, but it made no difference.