Should I use the word 'and' before the word 'hence' ?

you can use "and hence" if you choose.  It depends on the situation.  I heard gunshots, and hence I ran.  I heard gunshots.  Hence, I ran.  There was too much lemon in my drink and hence I grimaced.

No. "Hence" is outdated, but still used in very formal sentences. It's a conjunction that joins two clauses. You don't use it with another conjunction such as "and".

It's rainy today; hence, I can't work in the garden. 

It is okay indeed.

If something came before and it is appropriate, sure. However, you could also start a sentence with hence alone.

It isn't really needed, no, you could say 'and further more...' and that would work if you needed an alternative.

It is not necessary to use ‘and’.  It makes your sentence awkward.