Personally, I would use MB and stay away from blocks. Also, Those things you quoted are only guidelines and minimums.
In my environment, we do it like this. Remember these are only one way to do this. Also, everything depends on the OS flavor and whatever you have running on the box and how big of a system it is.
/ .................250MB.
/var ............1600MB. ( 1.6GB)
/usr.............1600MB.
/opt.............1000MB.
/home..........500MB to 1.5GB
/tmp.............2000MB to 4000MB ( 2GB to 4GB) Depends on demands of Application running on box. Link /var/tmp to /tmp so /var doens't fill up.
That adds up to 6.5GB to 8GB, which leaves 2GB to 3.5 for other things.
primary swap ( at least 2x to 3x of RAM) and 2ndary swap for OS same size as primary swap.
also, have a root swap in the root volume and another secondary swap for everything else.
dump space ( at least 30% to 50% of RAM)
crash space ( same as dump different place) Some OS are configured to use swap space as crash for system crashes. I would use the secondary swap, not root swap.
Hope this Helps you.