Regarding why Muslim wonen and men are so segregated and more...
Islam has no such practices. Unfortunately Muslims today have deviated from the original path and perhaps that is why they are in the state they are in.
Some facts that may help you:
1. Muslim men and women would pray together at the masjid, men at the front and then children and then women. Not indicating any hierarchy but for practical reasons. There was no "boxed" separate section for women as is today.
2. Muslim men and women would get together in the masjid, sit together and solve the problems of the community.
3. For a long time, Muslim women would be Islamic scholars. It is said that about 20% of all Islamic scholarship is by women. Women would teach in masjids to both men and women. It is sad that today there are barely if any female Islamic scholars (nearly 0%)
4. You may find more with Muhammad Akram Nadwi in his book Muhaddithat.
I hope that helps. Peace and blessings be upon you, and may Allah bless you in your search for the truth, and for His Message.