Agree with alot of the above .
If i were you id start at 70 mph on the machines . Pitched where you know it will be , then have the feeder dial up 2/3 mph in the same spot mixed in with the 70mph stuff (without telling you). Then go to 70mph with variation in line and length. Then have then feeder dial up 2/3mph in varied lines and lengths mixed in with the 70mph stuff . Then once you are comfortable with that (it may be one session , it might be a few -and thats ok) have your starting point at 72/3 mph and repeat the process. It shouldn't take too much time until the starting point is 80 odd.
Perhaps shorten your backlift a touch . Think defense first (better to nail your defense at high pace then get nailed by high pace) and with more exposure and increased reaction time the shots will come back sooner or later .
Also, something i found helpful when i returned to cricket about 5 yrs ago and went through this process myself was to 'armour up'. I got the best protection i couod and started facing the machine with a chest guard and arm guard too (a neck guard is something else that would be in this catagory). I know many people who frown upon this but it allowed me to have the cajonas to get up past 80+ mph again after so long out . I had faith in my protection and just told myself 'youve got no excuses to not get in line now'.
Anyway , 5 yrs on and i wear my arm guard and chest guard whenever i bat , matches , nets , machines , pace , spin ..... i like the idea/feeling of always padding up with the same type of kit and ive gotten used to wearing these items . I dont find them heavy or cumbersome . I sweat like a pig in aussie summer heat .....but id do that even wearing minimal protection so its kind of a moot point for me .
Basically , incremental adjustments in pace and wear whatever protection you need to build confidence.