I'm asking here since I didn't manage to find a definitive answer to my questions.
1. When should I use には and when は?
The only thing I managed to find online is that は is used when a quantity is involved as in
私{わたし}は犬{いぬ}が[四匹]{よんひき}います。
while には is used in every other case. [1]
However, the above phrase does not necessarily express possession. Out of context, it can simply mean "For me, there are four dogs", for example as an answer to "What's over there?".
2. Why is it wrong to use the particle に instead of には or は?