Your images are linking to attachment and not linking to media file.
Please edit your gallery.
For example, look at the gallery settings in the following screen-shot.
Regarding your customizer not loading.
Are you using the reduxframework plugin?
If not, Please install and activate it.
If you are still having issue with your customizer after activating reduxframework, you will have to disable one plugin at a time to find which plugin is causing conflict.
if it does not work, disable all other not required plugin and see if your customizer loads.
If it loads, then your server does not have enough memory to run customizer with all your plugins activated.
You can either remove some plugins or contact your web hosting company to increase your server memory.
At the mean time, you can use Appearance -> Theme Options which is more stable and requires less memory.