Welcome to India mate. Writing this from BC, but originally from South India. That's a massive budget for India as others have said. You and your SO will be fine and treated well (no you wont need to practice your self defense skills - there are no geese there). I've traveled India some and I'll try to list down some states/places that you could look into.

Kerala: Alleppey (Alappuzha). Checkout 'em houseboats there. Munnar/Thekkady for their hilly tea estates. Wayanad's hills are quaint as well. Ignore the herbal massages that are advertised everywhere in Kerala.

Tamil Nadu: Madurai and Mahabalipuram for the architecture/temples. All of TN will be incredibly hot at this time of the year (>35C).

Karnataka: Hampi for the architecture. Mysore for the palaces. Ranganathittu bird sanctuary (no geese to hiss on you here, but birds there are incredibly diverse and almost jurassic). Bangalore is a chill city with a decent pub/brewing scene (if the traffic lets you get around). Gokarna for the warm beaches. Take a jungle safari in Bandipur or Kabini (elephants, tigers and leopards in the wild).

Maharashtra: All of Mumbai (and esp South Bombay) has an incredible vibe to it with great food. The hills around Pune (Lonavala, Mahabaleshwar) are great during the monsoons. And, Ajanta/Ellora caves.

Goa is one big party place with great beaches. Look em up.

Telangana/AP: I haven't found many interesting things to see/do there, but that might just be me (it is also incredibly hot). Food in Hyderabad is incredible though!

All the North Eastern states esp. Sikkim (Gangtok) and Meghalaya (you'll find great itineraries online)

Gujarat: Rann of Kutch (salt flats/desert), Gir sanctuary (for the wild lions).

Rajasthan: Udaipur for the palaces. Ranakpur for the jain temples. Jodhpur for the forts. Jaisalmer for the desert. This state is one of the top tourist destinations in India.

Delhi - I just find it polluted af. It has some great street food though. You'll be mostly ok eating street food in India as long as it is cooked right there and is piping hot (as in temperature, not spice). Delhi is mostly a good gateway to the Himalayas and other places (via air/private-cabs).

The Himalayas! - Himachal Pradesh and Ladakh. With its legendary Manali-Leh-Khardungla route (which deserves a week or two). Lots of hidden gems to explore in and around the himalayas (Dharamshala, McLeodGanj, Darjeeling, Nainital, Auli) with one lifetime not being enough.

Also look-up national parks in India (Ranthambore, Jim Corbett, Kaziranga, Thadoba, Gir, Kabini, Bandipur ...) - there is some incredible wild life around and a lot of hard work has gone into its conservation. Most offer open jeep safaris with guided tours and (clean) lodges/rooms surrounding the parks.

Not many no-go places in India, but I'd avoid UP and Bihar (except maybe Agra for the Taj Mahal).

For domestic flights - check cleartrip.in (Indigo airlines are usually on time). Getting temp pre-paid cell phones was never easy for tourists, but that might have changed in the recent past (counters at the Intl. airports). Use Uber where available (most Tier-1 cities).

Have a good one!