The infection from an abscessed can most certainly spread . Body aches would feel like aches you get when you have the flu. The doctor was partially right in that if the infection does become systemic you could die but that is not always the case.
The initial symptoms of spreading infection would be localized around the tooth and related tissues. There would be swelling and exudate, possibly a boil and next there would be bone destruction. When the infection spreads beyond that and enters the blood stream you may experience fever,chills, lethargy, general body pain,pain in the tooth and redness and swelling around the affected area.
Beyond that would be a condition called sepsis and that is life threatening. The degree of difference small and can escalate quite quickly and that is why we advise immediate treatment for any abscessed tooth.
Even before sepsis, if a tooth infection lingers , complications can include heart murmurs, night sweats, weight loss, fatigue, aching joints and more.
I am not sure what kind of test the doctor there ordered.Bacteremia diagnosis
would need several blood cultures taken over several hours to discover. He probably just looked for an elevated white count in a CBC and that is a reasonable first step but not always diagnostic. I will agree that this would have escalated rapidly if you indeed had sepsis.
Suffice to say the tooth need to be treated now and best to get it done asap.