galactic questions

Just listened to Melvyn Bragg's latest-but-one podcast (which sadly being the latest-but-one I can't meaningfully link to now) on galaxies and had to listen to it twice in order to grasp a lot of things. If I stop concentrating for a minute on astronomy I find it very easy to lose track because all the facts and numbers are so, well, astronomical. But I was left with a few burning questions (which pretty much any amateur astronomer could probably clear up for me).

1. If (as per red shift and Hubble's Law) every other galaxy in the universe is getting further away from us, then why is Andromeda going to crash into the Milky Way in a few tens of billions of years? Is the movement away from singularity not a uniform radiation from a point?

2. Apparently the kind of things we can see, the stuff made of the subatomic particles known to us, is only about 4% of the matter in the unverse. Of the rest, about 20-30% is "dark matter" , which is therefore hugle significant but mysterious. But no one asked - what about the other three quarters?

3. Glad to get straight that the universe is about 13.8 billion years old, the Milky Way about 13 billion years old (it still foxes astronomers how the galaxies formed so "quickly") and gladder still to learn that we are less than halfway through the projected life of the universe (an inference from the tens of billions of years that apparently still separate us from collision with Andromeda). But has anyone started figuring out how long they reckon the universe will last before everything sputters out (or folds up again)?

4. Apparently galaxies through "secular evolution" (i.e. even without interacting with other galaxies) very gradually "use up" the matter that originally comprised them. Why? And how? I found this point a little depressing. And what about the dark matter (and the even darker stuff)

Incidentally it made me think of Aubrey de Grey and his anti-aging and anti-death scientific crusade. More than any other argument I felt the action of the cosmos gave the lie to the notion that we could ever possibly overcome the natural tendency of systems to eventually shut down - if the sun's going to do it, and the galaxy, then surely us. What's more alarming is to think that we'll shut down the earth before time. But perhaps in the end we will only shut down the human species.