Please help me pick out schools to aim for and what I should do for the next two years

[GalladeAggron]

Hi, I'm an undergrad at an Indian B-School: the Indian Institute of Management, Indore. I'm in the dual-degree BA-MBA programme, where the first three years are a BA  concentrated on economics, statistics, mathematics and social sciences (officially the undergrad degree is called "BA (Foundations of Management)") and the final two years are the traditional MBA. I'm in the third year and I have not really done very well so far; my aggregate GPA is 2.9 so far (~75% as per the school's conversion) and I'm ranked smack dab in the middle of the class. The programme itself is fairly selective (takes 120 out of 20000 applicants) and the institute is ranked fairly well in the nation itself (generally ranks as 4-8 nationally). There is also an option of taking a 1-2 year sabbatical between completing the BA and beginning the MBA.

My grades are definitely an issue; I actually have an F in a Development Economics course (I was doing very well in it but then COVID happened and I couldn't attempt the endterm) and a low grade (1.9) in my Linear Algebra course. I try to think I'm not a bad student however; I topped my statistics course as well as my advanced mathematical modelling course and have some high grades in other subjects too. My issue was that I didn't care to study so far; I just had no motivation. Coming into my third year, I'm realizing my PhD dreams are in jeopardy and I will likely need to attempt a very drastic turnaround to get in ANYWHERE.

I don't think I'll have issues finding a decent job (and I'll need a job for a couple of years after MBA at least) but my aim is to join a PhD programme in the long run. I'm 20 right now, 22 by the time I'll be done with my MBA; I most likely want to go for a PhD in economics or finance; but even strategy and entrepreneurship seem like interesting research fields. I'm currently finishing a research paper with a prof for publication and I do have several research ideas which I want to take up after this one. 

Can someone help me with a) how to select a field to target for PhD, b) which schools should I be targeting, c) how do I effect a dramatic grade reversal in my final year of undergrad and my two years of MBA, d) what should I be doing in these next 3 years to maximize my chances of getting into a good PhD program (or a good master's) when I'm done with my MBA?