Exactly, the Rams were already down by seven. Had they been down by three, declining the penalty would have made much more sense, because it's still a one-score game if New England kicks the field goal.
Um, yes, getting the ball back only down by seven IS better, because you would only need score once to tie the game, not twice. In my scenario, you need one touchdown in 30-35 seconds -- certainly improbable, but not inconceivable. In your case, you're praying for a missed field goal and a score, or they make the field goal (much more likely), and you need a score AND a successful onside kick AND another score. That was their best shot? Are you kidding me?
And, on top of it, there was certainly no guarantee the Rams would stop New England to force the field goal attempt. Had the Patriots gained two more inches, the Rams never see the ball again.
I guess you must believe everything Tony Romo tells you.