Hello Son,

https://engineering.careers360.com/jee-main-rank-predictor

Use the above tool to find your expected rank. 

Well, this completely depends on the cut-off of this year. If you don't belong to the general category, then you surely will qualify JEE main, as the cut-off for other castes, always remains less than 70.

But in case you belong to the general category, there are fair chances that you'll qualify for JEE main because the previous year the cut-off was around 74. So chances for jumping it to 80+ are quite less. But nothing can be predicted, since this time the exam was conducted by NTA and not CBSE, therefore students were expecting a comparatively easy paper. Therefore, there are chances that the cut-off may go high.

In my opinion, you should prepare for Advance, because there are good chances that you'll qualify for the main level, and eligible for an advance. God forbid, if you don't qualify, trust me, all the knowledge gained will not go in vain. 

Use the below link to see the previous year cut-off trends:

https://engineering.careers360.com/articles/jee-main-cutoff

Hope this helps

All the best for results.