In regards to "all Israel" will be saved we need to look at what Paul is sourcing in his letter to the Romans:
(Isa 26:21 For behold, the LORD comes out of His place to punish the inhabitants of the earth for their iniquity; The earth will also disclose her blood, and will no more cover her slain. )
In the above the prophet is predicting vengeance for the shedding of "innocent blood" as per Jesus' claim against the Jews.
(Isa 27:9 Therefore by this the iniquity of Jacob will be covered; and this is all the fruit of taking away his sin: When he makes all the stones of the altar like chalkstones that are beaten to dust, wooden images and incense altars shall not stand. )
(Isa 27:10 Yet the fortified city will be desolate, the habitation forsaken and left like a wilderness; there the calf will feed, and there it will lie down and consume its branches. )
(Isa 27:11 When its boughs are withered, they will be broken off; the women come and set them on fire. For it is a people of no understanding; therefore He who made them will not have mercy on them, and He who formed them will show them no favor. )
In the above "Jacob" is purged by judgement, the fortified city (1st century Jerusalem) is destroyed, the unbelieving Jews/Israel are showed no mercy or favor and destroyed (cast out of the kingdom - Matt 8:12).
(Isa 59:3 For your hands are defiled with blood, and your fingers with iniquity; your lips have spoken lies, your tongue has muttered perversity. )
(Isa 59:20 The Redeemer will come to Zion, And to those who turn from transgression in Jacob,” Says the LORD. )
(Isa 59:21 “As for Me,” says the LORD, “this is My covenant with them: My Spirit who is upon you, and My words which I have put in your mouth, shall not depart from your mouth, nor from the mouth of your descendants, nor from the mouth of your descendants’ descendants,” says the LORD, “from this time and forevermore.” )
(Rom 11:26 And so all Israel will be saved, as it is written: “The Deliverer will come out of Zion, And He will turn away ungodliness from Jacob)
(Rom 11:27 For this is My covenant with them, When I take away their sins.”
Paul in Rom 11:26-27 is conflating Isa 27:9 and Isa 59:20-21.
Isa 59:20 clearly states that only those "who turn from transgression in Jacob" are included in the "all saved", the rest are destroyed/cast out of the kingdom. This occurred in the generation that heard him along with the destruction of the "fortified city" in 70 AD.