Taking percentage based commission

Q: I urgently need to know something before I fall into haraam dealings. Please tell me if my method of charging commission is permissible:

I have an online store where people can advertise their things on my website and I charge them on each successful transaction, so if something was sold for R100.00 I would charge R1.00 (1%)

According to the Hanafi mazhab we are allowed to take percentage based commissions from customers, I have collected numerous fataawaa on this Alhamdulillah. What I need to know is whether I can tell my customers this:

We charge 3% for any sales under R1 000, 2% for sales under R5 000 and %1 for sales under R10 000

Although no ambiguity remains and both I and the client knows how much will be charged at the end of the sale, I just need confirmation if is this permissible. See the case scenario below:

Sometimes the client will have something like "negotiable price" on his advert, so he would either sell it for R900 or R1 000 for example. Since I charge him 3% for sales under R1 000 and 2% for sales between R1 000 - R5 000, is this considered as ambiguity or is it permissible?

Another scenario:

Someone advertises an auction on my website. The price of the auction could be won at anything from R1 to R2 000 or more. Can I charge a fixed 3% on all auction listings so that no ambiguity remains as to what the seller will pay me? So that if the sale goes for R1 then I will get R0.03 and if it goes for R2 000 I will get R60

I am very cautious of falling into haraam activity and this is my income so I need it to be clean.

Employer installing surveillance microphones and cameras in the business

Q: My boss is going for umrah and I have been tasked with managing the business in his absence. While I was away over the weekend he installed a microphone listening device that he connected to the camera system. I understand that cameras are necessary and assist us in the event that customers have queries. I am unhappy with the listening device and feel that it is an invasion of privacy. What happens if I recieve a personal and private call from my wife? Please let me know if it is Islamically correct to use such systems to spy on staff and if I am justified in feeling unhappt about it.

Selling human hair

Q: A fertlizer called amino acid is prepared from the hair of humans, dog or any other animal. So we are planning to buy hair from salons and then sell to this industries who make amino acid from hair. Is it permissible?

Lineage of a child born through marrying one's mahram

Q: If a person married his mahram and children were then born from this relationship, will the nasab (lineage) of the children be established from the father? Likewise, will the ruling be the same in the situation where a person married a woman who was haraam upon him because of hurmat-e-musaaharah, ridaa'at, etc. Also, can mufti saheb please explain if there is any difference in the ruling if the husband knew that she was haraam or didn't know?