How does Victor behave before his wedding in Frankenstein?

The answer to this can be found in Chapter 22.

First, you need to remember that the creature has told Victor that he will be with Victor on Victor's wedding night.  Victor is now terrified that the creature will come back and murder him, possibly in front of Elizabeth.

Victor acts in two different ways because of this. First, he tries to act all happy so that no one will know that he is afraid. You can see this in the following quote:

...I felt my heart sink within me. But I concealed my feelings by an appearance of hilarity that brought smiles and joy to the countenance of my father, but hardly deceived the ever-watchful and nicer eye of Elizabeth.

But then Victor arms himself with a gun and knives. This makes him feel more secure, and so he starts acting a lot more like he normally would.

I carried pistols and a dagger constantly about me and was ever on the watch to prevent artifice, and by these means gained a greater degree of tranquillity.

In Frankenstein, what feelings does Victor have before his wedding?

The feelings Victor has, in Mary Shelley's Frankenstein, regarding his upcoming wedding to Elizabeth are very contradicting.  As seen in his response to Elizabeth's letter (from chapter 22) the thought of marrying her brings him great unease.

I will be with you on your wedding-night!” Such was my sentence, and on that night would the dæmon employ every art to destroy me, and tear me from the glimpse of happiness which promised partly to console my sufferings. On that night he had determined to consummate his crimes by my death.

Victor knows, since he destroyed the second creature and broke his promise to his original creature, that his wedding night will not be a happy one. Instead, Victor fears his wedding to Elizabeth because he knows the creature will be there.

ON the other hand, the thoughts of marriage to Elizabeth bring Victor feelings of "love and joy."

Sweet and beloved Elizabeth! I read and re-read her letter and some softened feelings stole into my heart and dared to whisper paradisaicaldreams of love and joy; but the apple was already eaten, and the angel's arm bared to drive me from all hope.

Unfortunately for Victor, his elation regarding the wedding is short lived. He fluctuates back and forth between feeling happy that he is making Elizabeth happy and making his parents' wishes come true (that he will marry Elizabeth).

Over the rest of chapter 22, Victor states many times his horror at his impending marriage:

I would rather have banished myself for ever from my native country, and wandered a friendless outcast over the earth, than have consented to this miserable marriage.

As the period fixed for our marriage drew nearer, whether from cowardice or a prophetic feeling, I felt my heart sink within me.

I shut up, as well as I could, in my own heart the anxiety that preyed there, and entered with seeming earnestness into the plans of my father, although they might only serve as the decorations of my tragedy.

In the end, Victor is far more fearful regarding his upcoming wedding than hopeful or happy.