A random "tsu" like that is a common rookie mistake, haha. That's a っ, not a つ. It's basically used as a grunt, like "oof," though more literally it's cutting off a sound.
Eh? Really? No way! Wow. That's crazy! Right?
Nice. Cool. I couldn't think of that many all-purpose short responses in that short a time if I had to. Neat. Awesome.
The "is he laughing?" comment about the "w" is because it's like "lol" in Japanese, short for "wara" (笑, laugh/smile). They'll type a bunch of W's after a sentence, like the title of this video:
After the first few pages, I actually thought this might be a manga based on 女神なんてお断りですっ... That's an untranslated LN series about a reincarnated princess named Tia (in her past life, Satia) who led a rebellion and killed off her royal family before ending her own life at the age of 15. But she...
I gotchu...
"Sorry to keep you waiting. We finally get to sleep together..."
"Yeah, we finally get to sleep together...wait... the heck are you saying!?"
"It makes me the happiest when I get to plop into bed with you, Saito."
"Are you okay!? Did you eat something strange!?"
"If I had to say... I...