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That is one meaning of てくる, sure, but only in cases where the action is movement related, really.
Other potential uses of てくる:
In both cases, I kinda reason it out personally as “to come to do verb; to come to continue to do verb” (context tells you which one it is). In this case, Takagi-san has yet to actually do anything to be an obstruction, so I think it’s the “to become~; to start to~” meaning.
This article on に lists a bunch of uses for it, so might be good literature to refer to when you aren’t sure what exactly it is doing. The section that is relevant here is “Marking Verbs Directly,” and even includes a section that talks about に違いない specifically.
The takeaway is that に違いない is translated similar to the に決まっている phrase, and it is formed much the same way.
Overall interpretation:
Literal:
“Undoubtedly (きっと), somehow (何かしら) to become an obstruction it is no different to.”
A bit more natural:
“Undoubtedly, (it’s) not different to (Takagi-san) somehow becoming an obstruction.”
And to put it in fully natural English, not caring about grammar, while also making it the answer to what he asked himself in the speech bubble previously:
“I am sure that she is thinking about somehow obstructing me!”
Disclaimer: “Reasonality” is where Cure Dolly and I part ways. I cannot wrap my head around what she is trying to get at it with it. This is one of the few terms she invented that made me go…why? Somebody who likes the term might be better suited to giving you an explanation, as a result, but I’m just going to explain わけがない as I understand it.
To me, わけ literally just means “reason”. I have not been able to understand why she felt the need to make up a word when that one is right there. Maybe to create an umbrella term because “reason” can be a lot of things, and she wanted to simplify, but coming from my mind, it just didn’t work for me. 
Enough airing my dislike about that, though. If you look at わけ as simply “reason” and tack on がない, it’s as simple as that:
“Reason does not exist.”
Or in natural English:
“There is no reason; there is no way.”
The してこない is tied directly to the previous 邪魔をしてくる. Nishikata is thoroughly convinced that Takagi-san is purely there to get in the way of his studies.
So してこないワケがない is literally:
“To not become (carried over from previous sentence: an obstruction), reason does not exist.”
Naturally phrased:
“There is no reason (for Takagi-san) not to become an obstruction.”
Or
“There is no way Takagi-san will not become an obstruction.”
It’s a little weird in English thanks to the double-negative in the sentence, but it works fine, and double-negatives are perfectly acceptable in Japanese, anyway.
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[Details=Chapter 2, Page 11, Panel 3]
So, I’m a bit torn on this one, honestly. わからなく is adverbial, which is throwing me on giving an explanation, a bit. My brain wants to treat it as a noun.
“Thank you, the thing called barely understanding (って) exists (implied ある).”
Or naturally, “Thank you, I’m barely understanding,” or “Thank you, I have almost no idea.”
I feel like that is the intended vibe of the sentence anyhow.
But I feel like it’s a sentence I’m understanding the meaning without being able to properly justify the grammar that gets me there (という nominalizing is perfectly fine and makes sense, but I’m not understanding why it isn’t just わかんない), which makes me hesitant to offer it as an explanation.
Maybe @ChristopherFritz can weigh in on this one.
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