Tanning potential? Please help?

Hi there! I pretty fair and i want to tan but the safe way so i don't look like leather when im 30. I grew up very anti-sun because of my mom who overdid it and ruined her skin and steered me right away from it. However i do want a nice summer glow and im quite sure you can achieve it with using spf 40 and 30 however i can't seem to bare the sun. The sun feels like its burning me although im not burnt and the sweating and sunscreen melting is just makes me feel gross. I stayed in the sun today for 40 minutes , 20 minutes for both sides. The second i ran out of there i looked very slightly red but after a while it faded to nothing or a very slight tan. If i continue this daily or increase it by 5 minutes will i eventually become safely tan? I'd tan before 12 pm using spf 40 (body) and spf 30 (face) ( it should be the other way around but it just worked out that way) AND one last question , is the color of your feet pretty much as tan as you'll ever get if you wear sandals a lot without sunscreen?