The token is 4/4. CR706.9d is indeed the relevant rule for determining the Demon-copy's power;
Apocalypse Demon's CDA isn't copied at all by the ability of
God-Pharaoh's Gift, and without that ability, there's no effect to apply in layer 7a. (This rule is what allows
Quicksilver Gargantuan to work sensibly when copying creatures with power- and/or toughness-setting CDAs, and yes, it also means that a Gift-copy of
Tarmogoyf would get a boost from
Muraganda Petroglyphs once the temporary haste wore off.) If MTGO is behaving otherwise, that's a bug.
It should be noted that there's also a second problem with your previous understanding: in addition to there being no effect to apply to the Demon-copy in layer 7a, there's also no effects to apply to it in layers 4 or 7b. (Or 5, for that matter.) The parts of
God-Pharaoh's Gift that make the token 4/4, black, and a Zombie are modifications to the copying process, and are therefore covered by CR706.9c:
706.9c Some copy effects modify a characteristic as part of the copying process. The final value(s) for that characteristic becomes part of the copiable values for the copy.
What this means is that the token is made 4/4, black, and a Zombie as part of the copy effect that's being applied to it in layer 1,
not in the later layers where effects normally alter those characteristics. While this doesn't matter in this specific scenario, it becomes very important if you start mixing in more effects, for two reasons:
Firstly, it means that effects that modify the token's type, color, or power and toughness will apply to it the same as they would to a normal creature: if you control a
Godhead of Awe, a
Shifting Sky set to blue, and a
Conspiracy set to Merfolk, for example, a
God-Pharaoh's Gift-token of
Tarmogoyf will be a 1/1 blue Merfolk no matter what the timestamps of any of those cards are.
Secondly, it means that anything that's trying to copy a
God-Pharaoh's Gift-token will see the Gift's modifications: if you
Clone a Gift-token-
Tarmogoyf, the Clone-Goyf will end up a 4/4 black Zombie, just like the Gift-token-Goyf.
(This same ruling also applies to similar copying-with-exceptions effects such as Embalm, Eternalize,
Hour of Eternity, and so on, with minor modifications to take into account exactly which characteristics each specific effect modifies or excludes from the copying process.)