The dynamics of the situation didn't allow overt aid to China. The isolationists wanted to "stop war" but didn't have a coherent program to do this. The argument over how to do this hamstrung their efforts and resulted in some rather ill-conceived efforts, like the oil embargo. FDR was trying to avoid war in the Pacific and this didn't help at all.
You'll note in the OP that FDR says that the Japanese will get oil from somewhere, and do whatever it takes to get it. Nye, Burton, et al., however, had to do something to show their constituents they were "working for peace". The fact that they came up with an apparently "neutralist" move that was actually a provocation just shows the chaotic character of the peace movement.
FDR could have send just about as much stuff to China as he did to Britain and Russia - the problem IMO was more on how to get or secure the $ for that "help" and the Kuomintang being orriented more towards Stalin and Hitler. Upon the Chinese/German breakup small support started to dripple in (e.g. Flying Tigers) since Russia had other problems then to send weapons to China. After Pearl these political concerns didn't matter since the US needed another Front in Asia.
Britain being engaged by Germany, with Holland, France out of the game - it was obvious were the Japanese would move in.
Placing an oil embargo on the Japanese before things escalate was IMHO a very smart thing to do.
That it couldn't prevent a war between the Japanese and the US is understood - but to my understanding FDR didn't forward it in regards to avoiding a war at all, since he wasn't interested in himself and the US being a bystander watching Sake San taking over Asia, or crazy Adi taking over Europe.
The question for FDR was, how to get the Japanese/American relationship to a boilingpoint were the US could appear as the one party being (1) attacked first, (2) having to defend itsself or (3) having to kick out the Japanese from further occupied territories. (The last version is the one he was certainly trying to avoid).
The oil embargo surely helped in regard to version (1) and (2) however didn't help so much in regards to (3).