can more than two arrows point towards the same state from other states in a DFA? Is something like this possible: 

You have state A,B,C all pointing towards accepting state D.
Is this allowed?
Where online can I find a list of rules that define how an automata must be drawn or conceived?
Yes, this is allowed (and in fact, you lose a lot of computational power without it)

here is a definition of DFA (both formal and as drawings) + an example