Maps and Images
There are several sites which have maps of Calcutta around the period you are interested in:
Bengali Cultural Heritage has maps from 1842 to 1910, including several from the 1850s.
Old Maps Online from the British Libray is a useful tool which allows you to select city and time period, including Calcutta 1854.
From the Survey of India, 1854. Source: British Library, Old Maps Online
The map below is only a little before your period (1842) and it is clearly labelled so it should be useful.
Source: Wikipedia / Public domain. You can also check this link for a larger version.
There is also this colourful map of the Fort William area from 1844 and an 1850 postcard of the area (see below).
English postcard, 1850, 'View of Calcutta from the Esplanade'. Source: Wikipedia
More images can be found, for example, at Old Indian Photos where there are several 1860s photos of Calcutta in the aftermath of a storm.
Available for free is Calcutta, Old and New: A Historical & Descriptive Handbook to the City which was published in 1907, but it also covers your time period.
You will find several other freely available books on Calcutta on the Internet Archive, including The Making Of A Colonial Mind 1857-1885 which focus on the Bhadralok ("Bengali for the new class of 'gentlefolk' who arose during British colonial times") of Calcutta.
Colonizing, Decolonizing, and Globalizing Kolkata by Siddhartha Sen has a section on colonial Calcutta, including several images from the 1850s and 1860s, but it looks like you'll need to buy it (unless you can get access here through an institution).