I can't remember . There is only 1 Iphone app as far as I know . Samsung user myself . Perhaps some in Apple forums might know of more RF signal strength apps. Sorry I could not be more help.
Just take your smart phone up there and look for best signal . Here are some apps you can use . Open Signal , Network Signal Info , Real signal . I believe they are free in the App store
Wilson / Weboost boosters need a donor signal of at least -104 to function according to their website . I would try tweaking the outside antenna location for a sweet spot to make sure it is operating properly.