Do a lot of people get rheumatic fever?

Not anymore. Since the development of antibiotics (penicillin in particular) especially in developed countries with adequate access to medical care the number of patients that develop rheumatic fever has decreased dramatically as streptococcal throat infections are better diagnosed and treated.
Depends. In the USA this has become very uncommon, but since it is no longer a reportable disease the statistics are not available, but prior to the 1970's when there were large outbreaks, the frequency was one per 100,000 population. Many doctors in the USA have never seen a case of rheumatic fever.