Sleeping inside the car has some pros and cons imho. During colder winter seasons it keeps you warm, but you need proper ventilation and that means keeping some windows open. If you don't have mosquito nets you will be attacked the whole night by those little buggers. On the other hand during warmer months the lack of real ventilation will make your car too hot to sleep in.
I completely understand that it's a safety choice for you. You can maybe compromise on that part with a few things:
* Bring a dog with you (if you have one or maybe one from a friend). It will be a perfect companion on all your trips and dogs will alert you if something is wrong (wild animals, strangers, etc..)
* Get yourself a tazer or some tear gas. If you're planning to do Africa it might come in handy.
Looking at your budget of 40k i would consider a Pajero (i know i am biased ). They are reliable, not too expensive, and made for the stuff you mentioned. That budget will get you one with some miles on the clock but as there are so many available on the market that have just been used as school dropoff SUV it should be very easy to find a decent one with acceptable milage. Agree with @Gaurav on the 3.8 if you have the option of choosing.
Welcome to Carnity !