Do genital warts increase risk of anal cancer in heterosexual men? if so how much? is anal cancer rare?

Low risk, no worry: Genital warts are not likely to increase risk of anal cancer in men without direct anal sexual exposure. Anal cancer rates have been rising, often due to HPV infection, but primarily in gay men and to some extent in women. Despite the increase, it remains rare, with only around 3,000 cases per year in males the US (in a population of 320 million) -- and most of those in gay men.

HPV: Genital warts which are caused by infections by the human papilloma virus are definitely a risk factor for anal cancer. There is often involvement of genitals and anus by that virus. Genital warts can be treated by a dermatologist with either topical medications or by surgical removal.