1991 Chevy Van CLANK! Whats wrong with my Chevy G20 van?

OK this is a two part question, as there are two strange noises that are coming out of my van.

The first:

There is a very loud metal-on-metal clank that I hear whenever I am backing up and apply the brakes with any kind of force. After this happens, it will happen again the next time I hit the brakes in drive. It sounds like there is quite a bit of tension being released, less like metal actually hitting metal. This has always happened since I bought the van. It has gotten progressively louder. Also, I am now beginning to hear the same sound when going over bumps and potholes. What is about to fall off my van? The pitman arm, idler arm, and lower ball joints were recently replaced, so I doubt these. Also, I remember the mechanic saying the tie rods won't need attention anytime soon, so I doubt these as well.

The second:
This has something to do with the shifter. This only happens when the van is in drive. It sounds like squeaking, much like birds chirping, slightly lower in pitch. It is rhythmic, fast, and repeating. There is a "sweet spot" in drive where this noise is not made, but it always shakes itself back to being noisy. This started, very faintly, about a year ago. In the last month it has gotten much worse / louder. Also, the sweet spot got smaller. What could be causing this? I have no idea about this one. The transmission has always worked, so I ignored it in the past.

How bad off am I?

-James