Using someone you have no trust in to install your alarm system seems a bit odd.
Trusting the control of your alarm system to an app is an equal or greater vulnerability if you think about it.
You seem to point a lot of blame towards the installer but this is how this manufacturer have there cloud system setup.
There is no invasion of privacy, I assume you required the app and these are the terms of it.
I think the above few posts cover how you can go forward. If that be with app or without, installer or not.