Addressing your last point first, this is the definition of chromosome from biology-online.org.
Chromosome: A structure within the cell that bears the genetic material as a threadlike linear strand of DNA bonded to various proteins in the nucleus of eukaryotic cells, or as a circular strand of DNA (or RNA in some viruses) in the cytoplasm of prokaryotes and in the mitochondrion and chloroplast of certain eukaryotes. Yes, bacteria only have a single loop of DNA. That is their chromosome.
Now, I since your first point was more of a suggestion, I won't address it, but I will address your second point. You ask me to imagine a gene that tells the cell to create an extra chromosome. First of all, there isn't one. Secondly, if there was one, and if the cell did create an extra chromosome, the cell would die or, in a multicellular organism, develop into a cancer, as extra chromosomes are all but certain to have a negative effect. Having an extra chromosome (or missing a chromosome) is called aneuploidy, a chromosomal abnormality that leads to negative effects. In fact, the word aneuploid is taken from the Greek words meaning "not","good", and "fold." Like I stated earlier, most mutations have negative effects, and aneuploid is all but certain to have negative effects. The only reason I am using the term "all but certain" instead of certain is because I am not an expert on aneuploidy. However, no article that I have read mentioned any benefits. An extra or missing chromosome may lead to cancers, down syndrome, or a number of other bad conditions.
Aneuploidy occurs during cell division when chromosomes do not separate properly between tow cells. Since bacterial chromosomes do not separate (since they are never attached) it would be highly unlikely (I'm only using "highly unlikely" instead of "impossible" because I am not, as stated before, an expert on the subject) for aneuploidy to occur in bacteria. If it did indeed occur in bacteria, the bacteria would be unable to function properly and die. If a bacteria did indeed have a gene with the marvelous ability to encode a protein that would make an extra chromosome from scratch, there would be no reason for the cell would not be able to replicate the extra chromosome, as the chromosome would react with the enzymes responsible for DNA replication just like any other chromosome.
The main weakness of your argument comes from the fact that there is no evidence for the existence of a gene capable of creating an extra chromosome, as such a gene does not exist today. In fact, it is probably impossible for a gene to create an extra chromosome, as genes are blueprints for protein, not nucleic acids. You ask me to imagine a gene that could something when there is no evidence that any gene could do what you described. Asking me to imagine a gene that could do what you said is worse than a Christian asking someone to imagine a God who could create everything. At least God is God, and by being God he is understood to be all powerful. If God existed, he could indeed create everything. But no gene could do what you said. You claim to be objective and only believing in the facts, but claiming such a gene to exist would require wishful thinking or a determination to assert evolution's correctness. If your explanation, "Imagine there is a gene..." is fine, then why would you be against someone saying "Imagine there is a God..."? Saying God did something is much better than saying a gene did something that it can't do. I can't imagine a gene that could do something that no gene can do. It simply isn't possible. Why do you say that you only pay attention to the facts when you come up with something like a gene that creates an extra chromosome? At least Christians admit they put faith in God.