If he does testify he will get the chair (actually a choice of lethal injection or the gas chamber).
No way. The evidence is not sufficient to convict him if he fights it. Not in the jury's eyes.
I would agree with you in that our own worst enemy is OUR OWN MOUTH.
The Prosecution can cross examine and get you flustered and confused, and MAKE YOU LOOK GUILTY in fronty of a JURY, even when you aren't. That is why the law says you do not have to testify at your own trial.