How should a heh with a schwa under it be pronounced in an intermediate position in a word? E.g. פדהאל, or נהדר
פדהצור is actually not such a good example, because it doesn't have a sheva under the ה; there's no question, then, that it would be silent (like the ה at the end of the words תורה, מצוה, etc.). Perhaps you're thinking of פדהאל (Num. 34:28).
As I understand it, there should be an audible puff of breath in these cases - i.e., "neh-dar" (not "ne-dar"), "p'-dah-el" (not "p'-da-el"), etc. The closest English analogue I can think of is the dismissive "aah" (as in "never mind").