you'll get a ton of growth from a couple sessions with a coach. just to get your braking and placement squared away.
this is a 1.56 lap of me a while back. i've done a little better, but i got lazy with track videos.
your biggest time sacrifice is on the roval. you need to be higher in the bowl when the roval starts to turn. as you feel the car not being able to sustain full throttle, gently (GENTLY) begin to roll off the throttle as you turn-in. stay about mid track until you can start adding throttle and you can "see" the exit that doesn't result in your car being into the wall. lol roll back into the throttle and let your speed carry you within about five feet of the wall.