"Will all be" or "will be all" or "all will be"?

As usual with "Which of these is correct?" questions, they're all correct.

But they use different constructions, and can mean slightly different things (though most likely they don't).

First, the plural These (whatever unpleasant events they are) is odd here, unless there's some special reason in the context (whatever that might be) to mention that there is more than one unpleasant event, while attempting to comfort someone. Ordinarily that would not be a useful approach. So we'll limit discussion to (renumbering for convenience)

1. This will be all over soon.
2. This will all be over soon.
3. This all will be over soon.

Except for the position of all, which moves, everything else stays put. And there's another equally grammatical position for all, as well:

4. All this will be over soon.

(1-4) can be used to describe the same situation, though they're not quite synonymous. (1) contains the fixed temporal phrase all over/all done, which means 'completely finished'; the other sentences don't invoke this idiom.

The last 3, on the other hand, are synonymous transformations. (4) is the basic sentence, with the quantifier all modifying the noun phrase (this, whatever it represents). Quantifiers (like all, every, each, some, few, many) modify noun phrases; they normally precede the nouns they modify, like adjectives (they have to come before all the adjectives, though)

• All (of) the big brown Victorian townhouses are for sale

Some quantifiers (including all and each, but not including every) can undergo the transformation called "Quantifier-Floating" (Q-Float for short), which allows these quantifiers to appear at ("float to") different adverbial positions. Essentially, it allows these quantifiers to masquerade as adverbs like reportedly, which can go in many positions, especially before and after the first auxiliary verb.

• All the big houses are for sale ~ Reportedly the big houses are for sale
• The big houses all are for sale ~ The big houses reportedly are for sale
• The big houses are all for sale ~ The big houses are reportedly for sale

Q-float also works for each, though the verb agreement changes because each is singular, whereas all is plural.

• Each of the houses/Each house is for sale ~ The houses each are/are each for sale.

but Q-float doesn't work for every:

• Every house is for sale. ~ *The houses every are for sale ~ *The houses are every for sale