「ことと」 in a list of actions (and だったろう)

Question

In a story I'm reading I found this exchange:

「違うことをする理由が、見当たらない」

鳥井{とりい}は彼女の後ろ姿を眺めて、そうつぶやいた。

そしてその言葉はまったく、そのまま当たっていたのだった。

数少ない違ったことはと言えば、彼女が何回かヒールの高いサンダルで走ろうとして、つまずいたことと、そんな彼女にナンパ目当ての男が何人か手を差し出したことぐらいだったろう。

As context, the main character and a friend are tailing this girl, and he is speaking about the differences with a man whom they tailed the day before; If I'm understanding well the various pieces, the various parts of the sentence mean:

数少ない違ったことはと言えば: speaking of what was different

彼女が何回かヒールの高いサンダルで走ろうとして: the girl run a few times with her high heels

つまずいたことと: stumbled (and I think 「と」 here is "and")

そんな彼女にナンパ目当ての男が何人か手を差し出したことぐらいだったろう: various men looking to hit on a girl like that offered her a hand

So the girl was different from the man in a few things, like she tried to run in high heels, stumbled, and was helped by guys trying to hit on her.

What I'm unsure about are the 「ことと」 after 「つまずいたことと」, and the 「ことぐらいだったろう」 at the end: why 「つまずいたことと」 instead that 「つまずいて」, and the 「こと」 after 「差し出した」? I understand they nominalize what comes before, and I guess the 「と」 (as "and") links 「つまずいたこと」 with the following part (since the author isn't using the て form to connect), but I don't understand the need for them.

Also, I guess 「ぐらい」 marks the events described as trivial, but also assuming that's right, why 「だったろう」 (which I found marks conjecture)? My guess is that he is just hypothesizing how the girl could be different, but those events don't happen, as anticipated by 「そしてその言葉はまったく、そのまま当たっていたのだった」 (which I read as "And then those word [not seeing a reason for her to be any different] were exactly right").

Answer 1

The basic structure of the sentence in question is:

数少ない違ったことはと言えば、AとBぐらいだったろう。
Speaking of what little was different, it was probably nothing more than A and B.
The only differences seemed to be A and B.

This ぐらい is like "no more than ～". だったろう is the same as だっただろう, and it just means "I thought" or "It looked like" here. There is no hypothesis in this sentence.

A and B need to be noun phrases, and that's why they have been nominalized using こと:

A: 彼女が何回かヒールの高いサンダルで走ろうとして、つまずいたこと
A: that she stumbled a few times trying to run in her high heeled sandals

B: そんな彼女にナンパ目当ての男が何人か手を差し出したこと
B: that some guys tried to pick her up and offered their hands

Please don't be misguided by the comma between 走ろうとして and つまづいた. It's just part of a long nominalized phrase.

Torii is saying there is essentially nothing different. The two events (A and B) are trivial to her and they don't change what she has to do.