Yes, the offset is done with other Bresser sensors as well. They even are using Fahrenheit values instead of Celsius, plus an offset of 90 degrees. I would concentrate first on the humidity, as that will be encoded as a single byte most probably.
In my Manchester lib (I know this here is PWM, not Manchester ;)) there is another technique applied: a "decoupling mask". Any data byte is first XORed with a 8-bit mask of 11001010b before being sent. May be something similar is used here, but I was not able to find one yet. I tried to XOR the bit pattern of a humidity value against the received data, apply the resulting mask (if there was one) with XOR to another message at the same spot to see if the resulting bit sequence would result into the humidity value for that second message.
But unfortunately I did not find a match in the last 16 bits - I stopped there since I did it manually and got tired noting down bits 