Strings must be with double quotes and you missed some commas
{
"proj": {
"id": "sinusoidal",
"lon0": 134.25
},
"layers": [{
"background": {
"special": "sea"
},
"styles": {
"fill": "lightblue"
}
}, {
"graticule": {
"special": "graticule",
"latitudes": 1,
"longitudes": 1
}
}, {
"id": "Aus",
"src": "myfile",
"simplify": false
}, {
"id": "trees",
"src": "myfile",
"simplify": true
}, {
"id": "crops",
"src": "myfile",
"simplify": true
}, {
"id": "depth",
"src": "myfile",
"simplify": true
}, {
"id": "states",
"src": "myfile"
}],
"export": {
"width": "auto",
"height": "auto"
},
"bounds": {
"padding": 0.02,
"mode": "bbox",
"data": [92, -44, 181, -2],
"crop": [112, -44, 154, -9]
}
}