If the 'ereb bôqer is "beginning and end" as you suggest, then yowm can be more than a single 24 hr " day"
No, I did
NOT suggest this. Please pay attention. I believe Daniel 8:14 refers to a literal 2,300 evenings and mornings, and should be translated that way.
Just as we change the meaning of yowm perhaps we do not have right usage of 'ereb bôqer
You can only prove this to a translator (linguistically) if you show contemporary usage (contemporary to Daniel) of the meaning you are suggesting. That's how linguists and translators do semantics ("the study of meaning"). You have not done that.
"Keil and Delitszch" is still the most trusted OT commentary on the Hebrew. (I have the set, but you can access it through e-sword). Here is what they say (agreeing with me; note their reference to contemporary usage):
"In the answer, עַד is to be interpreted as in the question: till 2300 evening-mornings have been, or have passed, thus: 2300 evening-mornings long, so (=then) the sanctuary is brought into its right state. צָדַק primarily means to be just, whence the meaning is derived to justify, which is not here suitable, for it must be followed by, from the defilement of the desolation. The restoration of the temple to its right condition is, it is true, at the same time a justification of it from its desolation, and it includes in it the restoration of the permanent worship.
"The interpretation of the period of time, 2300 evening-mornings, named by the angel is beset with difficulty. And first the verbal import of בֹּקֶר עֶרֶב is doubtful. Among recent interpreters, Berth., Häv., v. Leng., Maur., and Horm. (Weiss. u. Erf. p. 295) understand by its days consisting of morning and evening (twenty-four hours); others, as Bleek, Kirmss, Ewald, Hitzig, Wieseler (who, however, in his treatise, Die 70 Wochen, u.s.w., p. 115ff., defends the first explanation), Kran., and Delitzsch, are of opinion that evening-morning is particularly reckoned with reference to the offering of a morning and an evening sacrifice each day, so that 2300 evening-mornings make only 1150 whole days. But there is no exegetical foundation for this latter opinion. It is derived only from a comparison, or rather an identification, of this passage with Dan_7:25; Dan_12:11., and Dan_9:27; and therewith it is proved that, according to 1 Macc. 1:54, 59, cf. 4:52, the desolation of the sanctuary by the worship of idols under Antiochus Epiphanes lasted not longer than three years and ten days, and that from Dan_12:11 it extends only to 1290 days."