As ADTech mentioned, your signals are very strong, and you shouldn't need a distribution amp, but your test seems to indicate that you do.
If your antenna is mounted inside, the signals could be weaker than listed on the report.
The signals from my indoor antenna are about 20 dB weaker than my report.
Where is your antenna located?
Is it aimed at 94 degrees magnetic?
If it is inside, is it aimed at a wall or out a window?
An FM signal report based on an estimate of your location:
http://www.fmfool.com/modeling/tmp/4...1/Radar-FM.png
If electrical interference was causing a problem for 13, it would probably also affect 5. You can listen for electrical interference on an AM portable radio tuned to an unused frequency at the low 540 end or the high 1600 end of the dial.