Hi thank you for your question. Please remember to RATE my answer OK SERVICE, GOOD SERVICE OR EXCELLENT SERVICE so I can get credited for my time.
1. Yes a traffic offence is a criminal offence.
2. The UKBA will take all the circumstances in to consideration , but i do not think they are likely to refuse the application due to a traffic offence which occured 5 years ago.
3. Yes, if the UKBA refuse your visa you will still retain your current leave to remain in the UK.
4. No, each applicant is issued a visa on their own merit if you submit an application together then they will look at each application. If your wife is the main applicant and she is not able to obtain a visa then the UKBA may decide not to issue the dependents with a visa either. However, if you each have obtained rights to apply for ILR on your on behalf then they will look at each applicant and make a decision.
But I would not worry too much regarding the issuing of ILR. A speeding fine is usually spent within 5 years so an application after October 2012 would be more suitable.
I hope this answers your question, if so kindly rate my answer positively so I can get credited for my time.