What do we learn from "Havi'u Es Kol ha'Ma'aser... va'Harikosi Lachem Berachah..."?
Makos 23b: Beis Din enacted to bring Ma'aser 1 . (Hashem's Brachah shows that He agreed.)
Ta'anis 9a: This is the only Mitzvah in which one may test Hashem, Malbim - it is not a test, rather, Bechinah. In Nisayon, Reuven tests whether something has a attribute greater than Reuven knew until now, e.g. is gold drawn to a magnet. Bechinah tests whether something is like its normal state, e.g. whether gold has impurities. If Brachah was via nature and the Ma'arachah, this would be Nisayon, for nature cannot give more than its limit. However, I promise that I will shower on you Brachah above nature from My storehouse, which is unlimited. This is only Bechinah, to fulfill His word.
Malbim: This explains "Shuvu Elai v'Ashuvah Aleichem" (7). Bring all the Ma'aser to the storehouse, so it will suffice for the Leviyim who guard His house, and the Kohanim who serve in Beis Hashem. They are like His household; he must feed them.
Rashi (23b): Bring it to the Mikdash, in order that Kohanim will share it with the Leviyim. Alternatively, bring also from other species; the Torah obligates only grain, wine and oil.
Why does it say "vi'Yhi Teref b'Veisi"?
Rashi: Food will be available for those who serve Me.
Radak: Food will be available for Kohanim and Leviyim who serve Me. Amidst this, you will repent from the sins listed. If not, I will send a different punishment. However, if you will bring Terumos and Ma'aseros properly, I will send rain and Brachah on you.
What do we learn from "Ad Bli Dai"?
Shabbos 32b: You will be blessed] until your lips will wear out from saying 'enough'!
Ta'anis 22b: We do not pray for [removal of] an abundance of good.
Radak citing his father: You will not have enough Kelim and storehouses [to store the grain].
Malbim: Brachah of Shamayim has a limit. When it reaches the limit, Hashem says 'enough!' Hashem's Brachah is miraculous, without limit; He will not say 'enough.'
