Looking for a language that shares many similarities with Sanskrit in pronunciation(vocabulary similarities are a bonus)

[Jiwon]

Just go for Hindi.

While all Indic languages claim to be descended from Sanskrit, Hindi has many characteristics that make it more attractive than the others. To start with, it uses the same script as Sanskrit, unlike Bengali, Punjabi or Odia. You also said you want to learn a modern language, so that leaves out Pali and Apabhramsha which might be closer to Sanskrit.

One drawback is that the way Devanagri is read in Hindi is somewhat different from the way it is read in Sanskrit. This may sound a bit weird, but just think about the Roman alphabet we are using. The same arrangement of letters "Mutter" will be pronounced differently in English and German, even though it looks the same in script.

You'll also find more resources to learn Hindi than other Indic languages like Marathi and Nepali. Some of them are even free.
You can always get a feel of the language with "A Door Into Hindi", although I do believe that the lessons progress very fast.
https://taj.oasis.unc.edu/

[tussentaal]

Everyday Bengali is more Sanskritized than everyday Hindi which is basically Urdu.