Battery should be sized to meet standby req without knowing the system currents you can't size it correctly. I would go with the size you need. I'd also advise a decent brand, failing batteries kill panels. Nasty one fail faster and harder.
I'd also say it's the panel battery as its showing 0001
No I havnt.
Which unit?
Id say normal walk test would be to test it to the extremity of the protected area. I see a lot of other systems where 1 unit is used where 3 are needed
There is a product called konnected Iirc but I can't see the point of it when you can use a panel that can do it directly. You must remember our primary focus here is security and reliability. Most of the time isn't good enough in the security sector
Don't use home kit but I integrate with home assistant. Easiest way is to upgrade as its an 800l it's getting on.
Alternatively I'm guessing the voltage on the zone inputs is 5v. You may be able to pick that up into gpio or use trans relays.
Alarms should be kept seperate Imo from automation but the sensor info and armed status is great for presence detection
At the moment its watch this space im hoping after discussions with HKC for a mqtt option for the app. There is alexa options coming but i havnt seen those yet.
I currently use esphome and an esp 32 to connect all my i/o into ha while keeping the signalling going. You are right the sia options are not over ip so that wont help.
I use output modules connected to the esp 32 and a 3.3v relay card for the inputs