You don't need a comma before "that" because it is always restrictive, unlike "which" which can be restrictive (without a comma) or non-restrictive (with a comma).

You don't need the <a>. Also, teachers often recommend that a sentence not end with a preposition. In a university English class, such is a tragic error in a paper.

Ending with a <to> may be fine for colloquial English, but not for a formal English university paper. It depends on the context.

I would rewrite this sentence as:

<This is the sort of English with which I will not put up.>

Here, <up> is really an adverb, but <with> is a real preposition.

(In a Technical English class in university, you can't use <this> or <that> by itself without a substantive following it. Technical English, yes, is different from the regular English class.)

> Ending with a <to> may be fine for colloquial English, but not for a formal English university paper. It depends on the context.

No one ever said this sentence was supposed to be formal.

-> Today is the morning that you have been looking forward to.
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