Not sure your going to get an adjustable trigger that goes down that low.
I have tried to different complete trigger replacements in a 452, the Rifle Basics was poo, the Timney I still have
but it won't go that light, it's on the ragged edge at 1lb 6oz, mine is at 1lb 12oz and is very smooth and predictable.
The very best trigger to be honest is either a yodave kit and some very careful setting up, or an adjustable sear, more money
but quicker and easier adjustment, only really important if you are going to keep adjusting though I would have thought.
If you really do want it easily adjustable on a regular basis you should have bought a 453 with the set trigger.
As far as a mod goes, I have tried them all at one time or another, but for the money the Sac is tough to beat at £35.
If I was after something a little better at more money then the ASE Utra rimfire, but only for a .22, not worth it for HMR to my mind.
Neil.