Is it normal and acceptable according to halacha that the husband inevitably becomes unclean by coming in contact with his wife during niddah period? Or it is very shameful and considered abhorrent, sinful to do so?
Is it shameful, disgraceful, sinful for the husband if he comes in contact with the niddah wife/ new-mother. In other words, during childbirth, is it natural and acceptable that he touches her for any assistance and becomes unclean for a day, or it would be very rare and only accidentally or unlikely that one may frown upon being unclean. Lev 15.19 whoever touches her shall be unclean until the evening; and for the new-mother, the man would most likely not touch her until her full purification period of 33 or 66 days completes.
wiki: Impurity after child birth
Within the realm of Biblical law and post-Biblical Jewish religious discourse surrounding tumah and taharah, the impurity is called in Hebrew tumat yoledet. Halakhah treats a yoledet (woman who gives birth) similarly to any woman with niddah status.
In some Jewish communities, ceremonies and a degree of seclusion were applied to postparturient women. For example, there was a Sana Yemenite custom of women visiting the mother during 4–6 weeks after childbirth. The mother would be visited in a special room in her home and she would sit in a decorated triangle box
Post English translations of all your quotes and try to cite old sources. I am asking for historical Jewish practice, not the modern culture which wouldn't observe such rituals.