Tricky - if you do have different views middle ground can be hard, but I suppose what's needed here is some form of compromise. I do agree with you though that it's a good idea to teach the value of money, responsibility etc.
The first problem I can see is that the youngest isn't working but does have her phone paid for - this could lead to the assumption that since your son isn't either at the moment, he should have his paid for too. (Although I expect you're hoping to encourage him to look for another job and take responsibility since he is old enough to work.) How about you give him the choice of recycling phone or repaying the line rental once he is working again? Explain the contract was based on him paying in the first place. The key will also to be to apply the same rules to each child at same age so no unfairness is perceived.
Also, I personally had to work from 14 due to a shortage of money. When my DD grows up I will encourage her to work too, but 15 is still quite young given he will also have GCSEs and A Levels to contend with at the same time. Again give him a choice - he can work for the extras he wants (which I did) or he can do without. Might you be able to pay him to work for you in some capacity? Like advanced pocket money?!
The next thing is the situation between you and your wife - a united front is crucial with kids or they get a wedge in there! Unfortunately the disrespect issue seems to be something of a modern malaise I must say. Your son and your wife will be constantly exposed to other teens talking to their parents like this both in reality and on TV and so will see it as normal - my DD is only seven and I've had to sort the same with her! I think I'd suggest discussing with your wife what she hopes to achieve as a parent. How does she want her son to grow up? How does she think he will be as an adult? How does she hope to achieve this? After all this is the purpose of parenting.
Now I was a strongwilled and could-have-been difficult teen but my mum dealt very cleverly with me. The truth is a teen IS capable of disobeying in a way that youngsters aren't. They can run away, they can get cigarettes, all sorts. I'd say the key is to make them feel you are on their side against the hormones and their own bad behaviour. So you need a mixture of house rules (how about for example, we all talk respectfully to each other? These could even be agreed on together) and also negotiation with a teen. Explain your reasons for things - after all you are trying to teach him to think for himself, not just to obey a parent, since you can't always be there. Explain the reasons why some things are a very bad idea, but try not to ban them - banned things = rebellion and therefore tempting!
Sorry I have rambled on a bit but what I am trying to say is, I think you need a compromise that you all agree to. So some house rules which everyone follows, and some allowance for the ages of the children and their growing independence. And remember a teen is trying to find out who they really are, and go through all sorts of (often not very likable) stages as they work it out. The best news is they grow out of it! Hope some of this is of some help to you, and wish you the very best with it - sounds like you have great integrity and are trying to lead your son into being a really nice young man!