I’m unsure, how helpful this is as you seem to be new to LuaTorch (rather Torch7) as well as PyTorch, but I would start with:

try to map each layer or operation to the PyTorch equivalent, e.g. nn.LookupTable should be nn.Embedding, nn.ConcatTable might not be needed as a layer and you should be able to concatenate tensors in your forward method directly, cudnn.SpatialConvolution would be nn.Conv2d, etc.
once this is done, try to recreate the model architecture by making sure the layers are called in the same order and their output has the expected shapes.