Now the first session of the fourth day is going on. India has managed to score 75 runs for the loss of 1 wicket in the second innings. The team has already taken a lead of 255 runs. India lost the first match. So the team definitely has a target of winning in the second match. Also, it will be sad if India cannot win even after taking such a big lead.

You are right that India should bat in two sessions today. Batting slowly will not be appropriate for India at all. And India should be given a target of at least 450+. If India is given a target less than this, it will be difficult for India to win.
Don't forget that India's opponent England is very experienced in the Test format. Even if India gives a target of 450+, England will try to win. So my guess is that India will not take any risk. They will want to give a target of 500+. If the batsmen can bat well, India will declare the innings with a lead of 500+. Otherwise, India will continue to bat until all the wickets are gone.