The 3rd image is mostly detailing his traing to become a flight engineer and wireless operator.
3 S of TT is No. 3 School of Technical Training which at the time was at Blackpool
4 S of TT was RAF St. Athan in South Wales, he went there twice
1661 CU is short of 1661 Heavy Conversion Unit, at the time it was based at RAF Winthorpe and trained aircrew who were converting to the Lancaster, Halifax or Sterling bombers as well as people like the one you are interested in.