Perhaps focusing on semantic differences between πταίω (stumbled) and πίπτω (fall) can overshadow a deeper meaning and end up missing some (if not most) of the real significance of what is written if the similarity between them is set aside. In other words, I think that first and foremost, both of these words plainly communicate a failure in Israel's ability to walk before God.
Then shalt thou walk in thy way safely, and thy foot shall not
He maketh my feet like hinds' feet: and setteth me upon my high
Whether it is stumbling or falling, each depict a transgression and separation from God, and it is this similitude between them that should draw our attention here in Romans 11:11, even as it does elsewhere in scripture where it appears to "double up" on what is being said. (Same as when we say the same thing twice, but in a slightly different way to try to emphasis the importance of it.)
Rejoice not when thine enemy falleth, and let not thine heart be glad
when he stumbleth:
...that no man put a stumblingblock or an occasion to fall in his
When viewed like this, the rhetorical question turns our focus entirely towards what God's greater purpose is (or might be) in Israel's horrific failure rather than it being a mere question of qualifying how bad or what depth of sin Israel's transgression is. Stumble or fall... they're basically one and the same. Both are bad, and have resulted in their being broken off from the root and fatness of the olive tree (i.e., separated from the richness of the believing that stems from Abraham), and the Gentiles (see verse 13) being grafted in.
 For I speak to you Gentiles...  And if some of the branches
be broken off, and thou, being a wild olive tree, wert graffed in
among them, and with them partakest of the root and fatness of the
Even if or when "stumbling and falling" are regarded as being nearly synonymous in this verse, there is enough written in the immediate context of Romans - as well as elsewhere - that it becomes clear that this stumble & fall is not forever. In fact, E.W. Bullinger suggests that the omission of "forever" at the end of the rhetorical question is a figure of speech called ellipsis. (see Figures of Speech Used in the Bible, E.W.Bullinger,D.D., p.23)
And they also, if they abide not still in unbelief, shall be graffed
in: for God is able to graff them in again.
Bullinger also refers to another figure of speech in this verse called prolepsis, and suggests that the question might be seen as, "Their falling away was not the object (or purpose) of their stumbling, was it? (ibid, p.980) This aligns with my perspective that in effect, these two words "stumbling and falling" should be thought of as being virtually synonymous.
Furthermore, this fall of Israel in verse 11 is focused on one failure, and one failure alone... their rejection of Jesus Christ. Not coincidentally, he is referred to as both a "stone of stumbling" and a "rock of offense" in 1Pet.2:8. After Christ's resurrection (aka, "the sign of the prophet Jonas"), the culmination of Israel's rejection is quite plainly evidenced in the council's stoning of Stephen in Acts 7:57,58. This inextricable binding together of Israel's stumble (their rejection of Christ) with Israel's fall (being broken off from the olive tree) can only be remedied with Israel's (i.e., what all remains of it) recognition and believing of Jesus the Son of God.
I am the vine, ye are the branches: He that abideth in me, and I in
him, the same bringeth forth much fruit: for without me ye can do
As for Romans 11:22, the severity to the fallen (i.e., Israel) has no distinct difference from those who stumbled (which again, simply refers to Israel.) From a historical perspective, whether thought of as a stumble or a fall, it appears that Israel as a nation was indeed dealt with severely. Perhaps the "kindness" in this verse 22 is a bit of a reflection of the kindness towards Abraham spoken of in Genesis 24:12-14. Whether that is true or not, the severity of God is directly associated with Israel (as a nation) being broken off because of unbelief. And likewise, Gentiles (as a nation) can (and will) be cut off because of unbelief once the fullness of the Gentiles be come in, and Israel grafted back in.
 And they also, if they abide not still in unbelief, shall be
graffed in: for God is able to graff them in again.  For if thou
wert cut out of the olive tree which is wild by nature, and wert
graffed contrary to nature into a good olive tree: how much more shall
these, which be the natural branches, be graffed into their own olive
tree?  For I would not, brethren, that ye should be ignorant of
this mystery, lest ye should be wise in your own conceits; that
blindness in part is happened to Israel, until the fulness of the
Gentiles be come in.
It is the goodness (or kindness) of God that leads anyone to repentance, although Israel (as a nation) is evidently temporarily blind to it.
Or despisest thou the riches of his goodness and forbearance and
longsuffering; not knowing that the goodness of God leadeth thee to
When Rom.11: 22 speaks of continuing in his goodness, perhaps it is perceived as a reference to anyone (Gentiles, namely) continuing to be led by His goodness to salvation. However, when the fullness of the Gentiles "be come in," said continuance will end. Hence, the remaining Gentiles (as a whole) will be "cut off" (as there are none continuing in, or led by, his goodness.)