K Rowling replies -> No. Voldemort as a father... now that's not a nice thought.
So for Voldemort and Bellatrix to have a love child is completely against what she had already said.
2) The Time Turner is not a device for bringing back the dead. It is well established that there is no magic that can bring the dead back to life. The closest thing we get is the Resurrection Stone and it doesn't really bring back the dead, it just makes their souls visible and tangible to whoever is holding the stone. Whenever the time turners are used in the books, they are never really used to change the present, but to allow for the present to happen. For instance, when Harry and Hermione save Sirius in PoA, they use the turners to protect Buckbeak, save Harry and Sirius from the dementors and free Sirius from the tower. We know for a fact that Harry cast his patronus before to save himself and Sirius, and we never see Buckbeak die (we only hear about the thump sound of the ax striking, which we learn was Mulciber swinging the ax in anger) and it can be assumed that Sirius was already free from the tower while Harry and Hermione were concocting their rescue plan with Dumbledore. Using it the way they did in CC flies directly in the face of everything Rowling has established.