Subway in Israel

Question

Hi, Thanks for the heter for eating in traif restaurants in Israel! My friend claims that Terumot and Maasrot are 'Deoraita' according the Rama. Since I'm ashkenazik do I need to follow the Rama on this as I do on other laws? During shmitta can I eat at the restaurant if they use heter mechira or yevul sheviit? Since Challah in Israel is more chamur - does that have any effect? thanks, sammy