The last time I made cake I used a recipe that used almond flour - with good results. AS far as thickeners - there are some made just for cakes, but I've never tried them.
Frosting is pretty easy - cream cheese, splenda, splash of cream to thin as needed, vanilla. Whip the heck out of it with mixer. Add other flavors if needed. Or frost with flavored whipped cream - easy breezy.