3.5 weeks, mostly in the south: what to add/scratch?

freshair

This is a rough itinerary. I still have a bout 4 days to add in between. I also list the main activities that i'm interested in. I'm looking for a good mix of nature and culture, not too touristy destinations and more well-known ones. Would like to know if i'm spending too much or too little time in each place, and if there's something i should add or scratch off. Thanks!

Date/place of (planned) arrival & departure.

Mumbai, arrive around 20 Dec and leave around 15 Jan.


Date/day of week of an individual journey.

20/12 (Sat) day train from Mumbai to Karwar or Gorkana (via Gao): a scenic route, or am I wrong?

21-22/12 Karwar/Gorkana: chilling, beach trekking. train to Kannur (via Mangalore)

23-24/12 Kannur: backwater trip, theyyam dance. is this enough time?

25/12 (Thu) Thrisoor: Kathakali dance

26-28/12 Munnar: trekking.

29-30/12 Madurai: getting the tourist dose

31/12 - 2/1 Chennai: Carnatic music and dance festival

after that, i have to options:
a: go up to Vizag, onto Araku/Jagdalpur, spend about 3-4 days to see tribal culture. Is it really worth it, b/c i'll take the train back to Mumbai via Hyderabad. I've already done the east-west route once (Kolkata-Ahmedabad) and not too sure about repeating it.
b: stay in TN and visit places like Courtallam, Kanniyakumari, and then make a couple of stops in Karnataka on the way back to Mumbai.

How many people in group, and what ages?

Just me. Female, 20.


Budget.

low budget ($20/day)


Preferred mode of transport.

train when possible: 3A if overnight, 2S or AC chair if during the day.
otherwise bus.

Daytime or overnight travel between places?

can be flexible.


Travel background.

am from Vietnam, but don't travel much in the country.
first time in India, but have been in Ahmedabad for the past 3 months. Have visited part of Gujarat (Diu, Sasan, Mt. Girnar) and Maharashtra (Ellora, Ajanta, Pune, Mahabaleshwar).


How flexible are you regarding your itinerary?

Somewhat.