With 84 percentile in JEE Paper 2 and an SC category rank of 675, you have a good chance of getting into some NITs for B.Arch, especially through the SC category and home state quota (Kerala). NIT Calicut is your home NIT, and you might get a seat there depending on the cut-off. You can also try other NITs like NIT Hamirpur or NIT Patna. Keep an eye on JoSAA counselling and fill in multiple options to increase your chances.