Issue with HDMI Arc connected TV

Dear experts,
I am running OSMC latest stable build on a RPi2. It is connected via HDMI at the HDMI arc input of my LG 55C7 TV. I also have a Hifiberry DAD connected to my stereo, but that does probably not matter here.
I use OSMC and Kodi for both audio and video. For audio use I do not need my TV, because I control kodi with Yates android app. I have two issues:
When I start the rpi2, OSMC seems to switch on the TV and/or automatically switches to the rpi2 HDMI input. I do not want this! Can I switch this off? I want to switch on and control the HDMI settings myself.

An even more annoying thing is that whenever I start the rpi2 with OSMC, the Live TV app of the LG TV gets confused. When I switch from rpi2 HDMI to live TV, the app does not start but crashes in an endless loop trying to get control (switching between app start screen and black screen …). After a long row of tests, disconnecting every hdmi input it is clear that osmc/kodi causes this problem. It does not appear when the rpi2 is disconnected or not running. I suppose there is a connection between my first problem described and the second. It seems that osmc constantly tries to get control over the tv and confuses the internal tv controls … somehow.

Any hints or ideas how to solve this?

Check Settings - System - Input - Peripherals - CEC Adapter - Switch source to this device on startup and other settings.