The RSSI is probably not working because the number is negative. I’m wondering if dynamic icons can support negative numbers because the - is reserved to separate the icon name from the state. I suspect it wont work so you will have to write a rule to change your RSSI Numbers to a positive value to use dynamic icons with it.
Icon filenames may include lowercase letters, numbers and underscores (_)
Uppercase letters and special characters are prohibited
from the docs I’m pretty positive you can’t define an icon for 1.5 or 1,5. You will either have to only use 1 and 2 or you will have to convert the value by multiplying by 10 and then you can use 15.