Maybe thinking Buddhism in historical context can assist in decyphering the cryptic anecdotes that Siddhartha may or may not have discussed, but "faithfully" preserved by his acolytes. Siddhartha, having been thoroughly discontented with the reigning Hindu religion and mystic yogis at explaining suffering, "woke up" under a tree, while in deep meditation.
Buddhism is likely somewhat of an anti-thesis to Hindu thesis in attempting to answer suffering. Thus, the elusive goal of attaining "nirvana," or nothingness/void, as opposed to the curse of infinite karmic cycle, to which Hindus are subject. Is Siddhartha posing a counterpoint to the Hindu creation belief of the abstract one god gazing upon himself by tuning the mind to subjective perception of the material universe?
Rather than gods and karma, Siddhartha seems to validate only the material and the subjective observer. The maya, or illusion, of existence in Buddhism seem to contrast sharply with the immutable fact of karma and caste. The non-existent self of Buddhism dictates the validity of man, which is denied by the objective externals and obligations of karma and caste.
I believe that to a certain extent he does, it would be necessary to see what nature he gives to the ideas to know if he places them in the same rank as the sensations, or if he gives a higher step as Plato does, however, both forms of perception are still inherent to the subject and therefore, following Buddhism, they must be transcended.
As for the material world, he refers to the All talking about the sensible and the intelligible, therefore, it is not about denying something beyond this, which could very well exist, but it shows the impossibility of perceiving something beyond this.
Furthermore, when he talks about ideas he may already be referring to something alien to matter, although again, it would be necessary to see what nature he gives to ideas.
And yes, I believe that both karma and caste Buddhism does not deny them, nor does it deny intellection and sensation, but it seeks to transcend them.