Mysteries of the Hebrew language

There will be a short delay while I work out some technical difficulties regarding some audio examples of "interesting" Hebrew. (Those fluent in Hebrew will probably roll their eyes, reading this post. But I never got past Intermediate in Ulpan, so some Hebrew still sounds odd to me.)

On the one hand, the link to Mark/PT's band website's Music page makes the Internet on my home computer freeze. So I have to set up the link to his wonderful "Ki V'Simchah" at the office. Done--here's the music link.

On the other hand, those who have the same problem that we have at home--that Mark's Music page makes our Internet crash--can listen to the same music here, where I choreographed my first dance to it, but I'll have to set up that link at home, because my office's 'Net Nannies block YouTube. Done--here's the dance link. (Hmm, I should have bent my arms at the elbow--I'm not crazy about the straight-armed look.)

So what does Mark's "Ki V'Simchah" have to do with "interesting" Hebrew?

"Ki v'simchah teitzeiyun,
U-v'shalom tuvalun . . ." (Yishaya/Isaiah 55:12)

Teitzeiyun? Tuvalun?

What the heck tense is that?

Here's one from another song by Mark, "Ma Yakar" (from his "Rock of Sages" album, available here and on iTunes):

"Ma yakar chasdecha, Elokim
u-v'nei Adam b'tzeil k'nafecha yechesayun
Yirviyun mi-deshen beitecha
v'nachal adanecha tashkeim . . . "

(That's from Psalm 36, verses 8-11, recited right after putting on a tallit.)

Yechesayun? How do we get from yechese (having to do with shelter or refuge, I think) to yechesayun? And yirviyun?

Then there's that line from Psalm 147, verse 20 (the last verse), " . . . u-mishpatim bal y'daum." Y'daum?

Here's a change of grammatical pace: Why does Psalm 148, verse 11 say "Malchei eretz v'chol l'umim, sarim v'chol shoftei aretz"? In both cases, it appears to me that the "s'michut" form (a type of possessive that creates an "of" between words) is being used. So why are there two different spellings? (Um, wild guess: "eretz" means earth, but "aretz" is a shortened form of "ha-aretz," the earth?)

Ah, the joys of being only partially fluent in Hebrew.