You could be right, but it is well known that enhanced DNA can be unreliable. I remember reading that the DNA found on Joanna's body would not have been enough to convict VT.
As far as him implicating the landlord is concerned, that is what the prosecution said, and VT was, indeed, given extra years on his sentence because it was said that he had done this.
Again, he MIGHT have done, but on the other hand, he might merely have wanted to help the police by giving them extra information. All the neighbours, when originally questioned, were invited to telephone the police "if they remembered anything else". Chris Jefferies did this, and was then arrested. VT did so, and was then arrested. Very strange!
Both Vincent AND Tanja (apparently) noticed that CJ's car was pointing in a different direction on the Saturday morning to on the Friday night, and they decided to telephone the police from Holland, having heard that CJ had been taken into custody. Some accounts say that it was Tanja who made the phone call, but it isn't entirely clear which of them made it. A police officer then travelled to Holland to interview them, and they took a sample of Vincent's DNA. The interview took six hours, and filled around 18 pages of the officer's notebook, so they can't just have been talking about CJ's car! Incidentally, this was when VT asked why the front door of JY's flat had been removed (he had seen this on the TV) and the officer became suspicious of him because he was taking so much interest in the investigation.
As CJ never appeared as a witness in court, we never heard whether or not he had, in fact, moved his car. I have not read anything that says he denied having done so. ( He does in the film "The Lost Honour of Christopher Jefferies", but parts of that film were fictional. ).
I cannot really see why it is implicating somebody to say that his car appeared to be facing the other way! If VT had really wanted to implicate the landlord, why not say that he had seen him letting himself into JY's flat, or that he had seen him talking to JY that night?