If you're normally running at +7, a 6dB attenuator would be spot-on as -7 is too low.
~3dB change in hot weather sounds about right tbh.
Is it a standard attenuator or an 'Forward path Attenuator'? - As your tx looks quite low (although I don't believe 34dBmV would be an issue persay...
For that packet loss, you wanna be looking at the logs in particular, as you'll see the T3 and T4 errors crops up
Tom