Ramesh,
Could you supply the exact references to the texts that you have extracted above, so that we can, for ourselves, read them in their proper context? It will also help us read the texts better if they are in front of us in Devanagari. Your Romanized Sanskrit is not only tedious to read, but apparently is full of errors as the meter in many places does not agree with the words.
Your further doubt is why is widow remarriage has not become fully acceptable despite the above text, which - presumably - allow it. My short answer would be the oft-quoted maxim शास्त्राद् रूढिर्बलीयसी, accepted convention trumps over canonical precepts. It is also said श्रुतिर्विभिन्ना स्मृतयश्च भिन्ना नैको मुनिर्यस्य वच: प्रमाणम्। धर्मस्य तत्त्वं निहितं गुहायां महाजनो येन गत: स पन्था:।, faced with innumerable rules which do not seem to agree with each other, the common man looks to the society leaders to find the correct path. Not everyone goes back to the first principles, the Vedas and the Upanishads, to order his daily life. People usually take their cue from what they observe around themselves.
The confined life of a woman in the male-dominated India society, of which there are countless evidences in our old literature, expected the woman to be the epitome of all virtue and the upholder of the family honor. Love and respect for her husband was expected of her. This, when stretched beyond limit, easily leads into requiring her to respect and cherish her dead husband's memory. Naturally, no remarriage for her after her husband dies! At the extreme, the convention also required her to follow her dead husband into the other world, though I believe that even in India of the 18th and 19th century, actual instances of Sati were rare. Sati was by no means a generally followed practice.
This, IMHO. is what happened with regard to widow remarriage.
(I would be particularly interested in looking more closely at the Manusmriti verses, cited by you. We know that among all such similar texts, Manusmriti attracts the most flak for social conservatism.)
Arvind Kolhatkar, Toronto, June 18, 2014.