1. no you do not have to go to 1.50 mater of fact if you do youve got a brick you just go straight to 3.71 m33-2 then update it either to -3 or -4 dont matter i always go up and dont skip
2. it dosent matter as long as you have custom firmware enabled
just go here
http://www.pspiso.com/showthread.php?t=176212&page=33. put your charger in turn it on let it boot up all the way and put your battery in then load up upms press x on battery tool then go down and turn your battery back normal then your done.
4. its called nand dump and you dont need it really but basicly if you want to all you do is press your []= square button to create it and read you screen
it tells you everything you need to do
if you use this one you might have to create your ipl loader again i did before it boots up cause it will stay a black screen (its the first option when you boot it up then go down and do that one and it works for fat and slim and on the fat it went straight to 3.71 m33-2 for me