I agree with having raise/lower on both sides. With both on the same side, one of them is going to be too far from the thumb resting position. With one on each hand, think which hand do you prefer and put the most probable layer (e.g.: numbers or function keys) on that hand. I would make the detachable top row layer-symmetrical with the main top row (there are two repeated keys in your layout).
I would place "the same" key in multiple places for easier combos: for example, arrows in HJKL (with left thumb), navigation cluster in arrows (with left thumb) and in ASDZXC (with right thumb), etc.
Based on your layout, I would suggest something like:
[{t:"#000000\n\n#00589f\n#00773a",p:"R3",sm:"cherry",f:4,fa:[0,0,2]},"\n\nESC\n\n\n\n~`",{fa:[0,0,2,2]},"\n\nF1\nQ\n\n\n1!","\n\nF2\nW\n\n\n2@","\n\nF3\nE\n\n\n3#","\n\nF4\nR\n\n\n4$","\n\nF5\nT\n\n\n5%","\n\nF6\nY\n\n\n6^","\n\nF7\nU\n\n\n7&","\n\nF8\nI\n\n\n8*","\n\nF9\nO\n\n\n9(","\n\nF10\nP\n\n\n0)","\n\nF11\n[{\n\n\n-_","\n\nF12\n]}\n\n\n=+",{a:0,w:1.5},"\n\nPrtSc\nBackSpace\n\n1.5u\n\\|",{p:"R1",a:4},"\n\nIns\nPause\n\n\nDel"],
[{y:0.25,p:"R3"},"\n\n~`\n\n\n\nESC","\n\n1!\nF1\n\n\nQ","\n\n2@\nF2\n\n\nW","\n\n3#\nF3\n\n\nE","\n\n4$\nF4\n\n\nR","\n\n5%\nF5\n\n\nT","\n\n6^\nF6\n\n\nY","\n\n7&\nF7\n\n\nU","\n\n8*\nF8\n\n\nI","\n\n9(\nF9\n\n\nO","\n\n0)\nF10\n\n\nP","\n\n-_\nF11\n\n\n[{","\n\n=+\nF12\n\n\n]}",{a:0,fa:[0,0,2,2,0,0,3],w:1.5},"\n\n|\\\nPrtSc\n\n1.5u\nBackSpace",{p:"R1",a:4,fa:[0,0,2,2]},"\n\nDel\nIns\n\n\nVol+"],
[{t:"#000000",p:"R2",a:2,w:1.25},"Tab\n\n\n\n\n1.25u",{t:"#000000\n\n#00589f\n#00773a",a:4},"\n\n\nIns\n\n\nA","\n\n\nHome\n\n\nS","\n\n\nPgUp\n\n\nD",{t:"#000000",a:6,n:true},"F","G",{t:"#000000\n\n#00589f\n#00773a",a:4},"\n\nLeft\n\n\n\nH",{n:true},"\n\nDown\n\n\n\nJ","\n\nUp\n\n\n\nK","\n\nRight\n\n\n\nL",{t:"#000000",a:6},":;","\"'",{a:2,w:2.25},"Enter\n\n\n\n\n2.25u",{p:"R1",a:6},"Vol-"],
[{t:"#000000\n\n#00589f\n#00773a",a:0,w:1.75},"\n\n\nCaps\n\n1.75u\nLShift",{a:4},"\n\n\nDel\n\n\nZ","\n\n\nEnd\n\n\nX","\n\n\nPgDn\n\n\nC",{t:"#000000",a:6},"V","B","N","M","<,",">.","?/",{t:"#000000\n\n#00589f\n#00773a",a:0,w:1.75},"\n\nCaps\n\n\n1.75u\nRShift",{a:4},"\n\nPgUp\n\n\n\nUp",{t:"#000000",a:6},"Volx"],
[{a:2,w:1.25},"Ctrl\n\n\n\n\n1.25u",{w:1.25},"Alt\n\n\n\n\n1.25u",{t:"#00589f",w:1.25},"Raise\n\n\n\n\n1.25u",{t:"#000000",a:3,w:6.25},"\n\n\n\n\n6.25u",{t:"#00773a",a:2,w:1.25},"Lower\n\n\n\n\n1.25u",{t:"#000000\n\n#00589f\n#00773a",a:0,w:1.25},"\n\nMenu\n\n\n1.25u\nWin",{a:4},"\n\nHome\n\n\n\nLeft","\n\nPgDn\n\n\n\nDown","\n\nEnd\n\n\n\nRight"]