Continuing a marriage if the mahr (dowry) has not been paid

Q: Is it permissible to continue a marriage if the mahr (dowry) has not been paid? 

I am currently married, but my husband has not yet paid the agreed-upon mahr (dowry). I would like to know if my marriage is still valid in Islam without the payment of mahr. What steps should be taken in such a situation? Is the marriage still considered valid, and what are the Islamic guidelines regarding mahr payments? Should I take any specific actions to address this issue?

Husband sending text messages to his wife: "Go, I release you" and "I have no claim on you; you can live your own life."

Q: My husband said to me in a text message: "Go, I release you" and "I have no claim on you; you can live your own life." 

Does this count as a valid divorce (talaaq) according to Islamic law? I want to know if these words constitute a clear divorce or not. 

Wearing underwear in the state of ihraam due to urine incontinence

Q: My father has a small problem with old age and urine drops. He says straight after he goes to the toilet, about 5 or 10 mins after, he has some trouble with few drops. Then it subsides. 

He usually uses tissue with his underwear for a few minutes after going to the bathroom in case any drops come out and then discards it a short while later. 

He's concerned with ihraam and how would he manage. 

What would be suggested? Is there an option to wear underwear and pay damm? Or is there any alternative.

Husband wanting to reconcile after sending divorce notices to his wife

Q: My maid has a situation. Her husband hit her and forced her out of the house two years ago. Then, two months ago, he sent her two divorce notices at the same and one notice saying that she is of bad character and he wants custody of the children. Now, five days ago he sent a third divorce notice. 

He signed the first two notices but didn't sign the third one. He said he did it because he wanted her to feel threatened and come back herself. 

After sending all three notices with the last one sent five days ago, now he wants to get back together. 

Is their Nikah still valid, or are they completely divorced now?

Husband giving the false impression that he was not married when taking a second wife

Q: My husband didn't clarify about his previous marriage to me in our Nikaah certificate. He mentioned that he was divorced from his previous marriage but after our marriage he disclosed to me that his ex is still his wife and I am his second wife. 

My question is that, is our Nikaah done or because of his statement our Nikaah is not valid? Please clarify.