Hi zero,
There is no option in the plugin to adjust the default Zoom. The only way would be to alter the plugin code for the embed. For example, in that same map.js file you referenced, you will find the following line of code:
bpMapIframe.src = '//maps.google.com/maps?output=embed&q=' + data.addressURI;
If you added Google’s zoom parameter to the end of this, it would allow you to change it. For example:
bpMapIframe.src = '//maps.google.com/maps?output=embed&q=' + data.addressURI + '&z=13';
You would then just need to change the 13 to whatever you want.
Please keep in mind that any changes you make directly to the plugin code will be overwritten if/when you udpate the plugin.