"I wish I were living in Korea by now"
There seems to be too many ways of saying it - I can't decide which one's the best :-)
1. 지금쯤 한국에 살고 있다면 좋았을 텐데 [좋았을 것을, 좋았으련만].
2. 지금쯤 한국에 살고 있다면 좋을 텐데 [좋을 것을, 좋으련만].
3. 지금 한국에 살고 있다면 좋을 텐데 [좋을 것을, 좋으련만].
#1 (past tense at the end) expresses a strong regret that I am not living in Korea by now.
#2 (present tense) shows a lighter regret, or sometimes even a realistic hope.
지금쯤 is like "by now" or "about now", while 지금 is plain "now".
So #3 means "I wish I were living in Korea now".
좋았을 텐데, 좋았을 것을[걸], or 좋았으련만 means "it would have been nice, while 좋을 텐데, 좋을 것을, or 좋으련만 is more like "it would be nice". But the difference is not always clear cut and people sometimes use them interchangeably.