2003 Dodge Caravan INTERMITTENT PEDAL PRESSURE

We have a Grand Caravan Sport (I think it's AWD) 3.8L Engine. I accidentally poured Power Steering into the break resovoir (Shoulda actually looked at the bottle before pouring) I tried to syphon as much out as I could when I realized what I was doing, But I am guessing it wasn't enough to prevent damage. I just topped off with Brake fluid and it was fine untill about a month ago.

- Pedal feels firm but loses firmness and sinks slowly to floor. Sometimes it stays firm and other times not

- Other times Pedal goes 1/2 to 3/4 of the way to floor and then gets firm.

- Sometimes it's strictly manual with pedal to the floor.

-Sometimes Pedal feels firm, sinks 1/2 way then brakes let go unless harder then they grip and unless I keep pushing they let go again.

- Pumping breaks does seem to help sometimes if done slowly as in tap let go, push let go, push let go But rarely.

- Fluid levels in resovoir remain full

- No Lights or indicators to show trouble

- Front Brakes changed in 2009