Could it be anything other than CEM?

I have a 2004 s60 2.0T, it has been well maintained by my dad for over a decade, and I've had no problems with it until 2 weeks ago, while I was driving on the motorway, I got a message saying 'ABS/Anti Skid Service Required' and the cruise control turned itself off. Since then I've had-

1. Brake Failure, Stop Safely (brakes work fine)

2. Check engine light

3. A sudden drop in gas mileage (currently getting about 20 mpg)

4. There is a loss of power as well

Took it to the Volvo garage and they said it could be a CEM fault but more investigation is needed to confirm, and Volvo says a new CEM costs £970 (far more than the car) I just wanted to see if it was worth investigating further or just cut my losses and write it off.

NB: I'm a student and I can't really afford a new CEM, but really need a car to go to hospital placements etc. I am wondering if it could be anything other than the CEM causing these issues, or if anyone has experienced this in the past. I would be very grateful for any help.