Take the battery out and remove the alternator and have them load tested at your local auto parts store (free). As far as the turn signals...sounds like a ground issue I had. As far as the starting problem...could be alternator not charging/low charging or a bad battery.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
