Do Androids Dream Of Electric Sheep questions

I've got some questions regarding Do Androids Dream Of Electric Sheep.

Warning: If you haven't read the book, the following gives away some
important points.

1) Does anyone know what the zygote-bath DNS factors are. Rachael mentions
these in the hotel room with Deckard. Their topic of conversation is the
Voight-Kamppf test, which, through modifying these Zygote-bath DNS factors
the Rosen Association will eventually create an android which is
indistinguisable from humans.

2) I don't fully understand Mercer, in particular the rocks hurled at people
while using their Empathy Boxes. Equally baffling is where Mercer appears
to Rick Deckard and warns him Pris is on the stairs, waiting for him.
Also, there is a wild scene where Isidore, after hearing Buster Friendly
expose Mercer as a swindle, and uses his Empathy Box, experiences the world
practically collapsing. Is this his imagination, or something else?
Also again, Mercer tells John Isidore if you kill, you can have nothing
to do with him. Yet to Deckard he tells him he must continue to kill. This
sounds to me like the voice of one's conscience. Then there is the matter
of the reconstitued spider.

3) What happened to Phil Resch? Does he go to work for the Police on
Lombard, or does he vanish into thin air?

4) After Rachael settles down to listen to Buster Friendly's expose on the
radio, the chapter ends. In fact it ends thus; "Her victory over him." Him
being Deckard. The reader returns to J.R. Isidore's apartment, and the
androids watching Buster Friendly's expose of Mercer. Next moment
Deckard is outside John Isidore's apartment. What happened in the interim?
Why, after Rachael was certain she had prevented him going after the
remaining androids does he suddenly prove her horribly wrong?

Did anyone else find Deckard a pain in the rear, particularly by the end? I
was reading the part where Mercer warns Decdkard about Pris, and all I
wanted to do was throttle the old beggar.
Pris would have killed Deckard, but he's no great loss. The only
problem is another bounty hunter would take his place.

Deckard isn't the most intuitive person, either. In some important cases,
he's remarkably obtuse. He fails to understand Rachael killed his goat as
the only means of getting back at him. You killed my friends, you took
something precious from me, I'm killing your animal, I'm taking something
precious from you.
That's revenge philosophy, which is exceedingly human. We've seen it in
a lot of cases, especially in the Middle East. It is horrible, but it
sometimes all people have. Sadly.
He's not particularly kind to John Isidore either. His attitude to
"chicken heads" is derogeratory to put it mildly. And if he's the best
humanity has to offer, God help us.

Sorry if this is a bit long winded. All help is appreciated.