Speed is the methamphetamine made from crushed sudafed
That comment is completely misleading - most meth made in Australia is made from crushed sudafed (base certainly is) - the purity at the end of it depends on the cook's skills, conscience and the number of dealers' hands the drug has passed through.
He is pretty accurate on the purities though - "Ice" is definitely almost exclusively imported from Asia although is rarely 90% (Maybe when it arrives here) 80% is the highest it will get. Obviously if your Ice is cut or melted down and recrystallised with MSM it could be far lower.
5-20% is just cut down methamphetamine - calling it speed is unhelpful. This quantity could have started life out as "ice" - i.e ~80% meth or "base" - i.e. meth ~40% pure before being cut down. If it is still pretty strong and bone white it probably began as "ice".
Again you could have 80% "ice" cut 1:1 with glucose making it 40% - you certainly would not describe that as base however.
"Base" at 40% again is misleading. Paste methamphetamine is often around this amount - 30-50%. HOWEVER Paste can actually be anything - the cook may have completely BLOWN the synth - you might have 10% methamphetamine and 90% impurities (as in 10% pure at the end of the synth - just a sticky brown mess) and many of those would be rather toxic/harmful.
One of the best ways of testing methamphetamine (aka base/speed/ice/rock/goey etc etc etc) is to use the Extreme Tester. Simons will confirm it is methamphetamine (99% of the time it will be) and Marquis gives and excellent indication of purity. Generally crushed "ice" will smoke and fizzle to orange in an instant. (If this doesnt happend your tester is too old or someone has interfered with your ice - see MSM reference)
Other forms base/speed will change at varying rates depending on the purity and amount of cutting agents employed.
The other famous test is of course the taste test - generally for base/speed the more bitter the more stronger. The same holds true for "ice" however bitterness may be from cutting agents such as MSM. The point is though methamphetamine as a chemical IS ALWAYS BITTER. You cannot hide it, or change it. Therefore if it aint bitter it is not of high purity. (Just remember though if it is bitter it does not mean it IS of high purity)