Welcome.
ad.1
The barcode reader sends the string to the computer. So if you set the ABMInput field as text, on which the cursor will be positioned, after pressing the reader button, the read string of digits will be sent to the Input field as if you were typing from the keyboard. Then the method of reading the ABMInput field change will win that there is something new and will execute your code.
ad2.
Yes you can. I did it for a client. After pressing ABMFileInput component there is a selection that is from the camera. The captured photo is quietly saved on the disk. Since you can write to disk, you can safely save to the database. Tested on Android.