The Farnborough book has an Appendix 6 detailing the "accelerators" installed on each British carrier from 1935 to 1978 and the specs of those devices. It doesn't give the steam pressures, just launch weights and end speeds and for the steam catapults the length so probably not what you seem to be looking for.
Don't forget that when launching an aircraft one limiting factor is the G forces applied to the airframe and crew. No point in using all that steam pressure to boost the aircraft, if the end result is that the crew black out on launch, the wings come off and the fuselage sails off into the briny for the carrier to run over it!
Look at some of the test work done on the new EMALS catapults on the USS Ford. For a while it couldn't launch Sea Hornets with drop tanks. https://news.usni.org/2017/07/28/emals-fix-finalized-reduce-stress-put-heaviest-airplanes-ford-class-carrier-launch
So the planned BS.6 (250 ft long) in CVA.01 could launch a 60,000lb aircraft at speeds up to 150 knots, or as a minimum 15,000lb at 110 knots, without exceeding 5G. That allowed the launch of unreheated Phantoms and Buccaneers and a margin for the prospect of heavier aircraft to come. While doing so it was intended that her speed capablity should not drop below 25 knots (from 28 knot max) through diversion of steam to the accumulators.
By way of comparison the C-13-1 & 2 catapults in the Nimitz class have a stroke of just over 306-310 feet and are capable of launching 80,000lb at 140 knots. They exert something like 4G initially dropping to 2G at the end of the run. And today's aircraft like the F-18E/F are actually lighter than the A-3 Skywarrior and F-14 Tomcat of the past. AIUI one of the advantages of nuclear power is that there is enough steam available to maintain speed while launching aircraft unlike in a traditional boiler powered carrier.
That is the fascinating thing about carrier aviation. There is a symbiotic relationship between the ship and its aircraft.
Edit:- The other think to remember is that in modern carrier aircraft all the force applied by the catapult shuttle passes into the airframe via the nosewheel leg and not cables connected to catapult points in the fuselage or wings.
