I would be leaning more to Atropurpureum. Your photos show the familiar greenish tints that comes in Summer and variable size leaves compared to a Bloodgood cultivar that holds its deep reds and especially in a lot of sun.
I think both 'Atropurpureum' and 'Bloodgood' are amoenum. ... But I call all my "Japanese maples" "palmoenum", particularly those grown from seed. <LOL>
Looks like Acer amoenum to me. The large size of the leaves is a definite identifying feature too. If present, flowers and fruits will be larger also. If there are any fruit the samaras will be 2.5-3 cm long for amoenum vs 1.5 cm for palmatum.