Your question mentions two different issues. In this answer, I would like to confine myself to the second part of your question, namely the issue of the significance of the fifteenth night of Sha'ban, often referred to as the night of bara'ah.

Let me state from the outset that it is a highly contentious issue among scholars. One group attaches great importance to reviving the night of mid- sha'aban while others consider it as a bid'ah and innovation to be  shunned. The first group cites a number of traditions extolling the excellences of this night, none of them fulfills the criteria of attestation of traditions established by the critics of hadith.  However, those who value this night say that such traditions by the sheer number reinforce each other, and hence imply the excellence of the night. Others, on the other hand, reject this reasoning.

Imam Nawawi has this to say about reviving the night of mid-sha'ban with special prayers: "The salah, known (among the late comers) as salaat al-ragha'ib, which entails praying twelve rak'ahs between maghrib and 'isha on the first Friday of the month of rajab and praying one hundred rak'ahs during the night of mid-sha'ban, both of which are  reprehensible innovations. One must never be deceived by the fact that it has been mentioned in works such as qoot al-quloob and ihya ulum al-ddeen nor by the traditions often cited in this respect; for it is baseless. And don't be deceived by the fact some eminent scholars have also been confused about it ... as they are mistaken in it."

 Among those who vehemently argued against it was Shaykh Izz al-Ddeen ibn Abd al-Salam, known as the emperor of scholars, while Hafiz Ibn al-Salah was among those who argued in favor of it.

On considering the arguments of both sides, one point emerges clearly: It was definitely not a well established practice inherited from the Prophet, peace be upon him; if it had been so, it would not have been so much contentious. There is no mention of the Prophet setting aside this night for any special prayers either by himself or in the congregation. If he had done so, it would have been reported widely by his companions who were eager to pass on to us everything he had said, did or approved of as part of religion. We believe that the Prophet has taught us all the rituals of worship clearly. No one can say that reviving the night of mid-sha'aban with special worship is one of the such practices.

There is a lot of wisdom in Imam Malik's policy, who, we are told, when in doubt held on firmly to what has been clearly established. Imam Shafi' said of his teacher Malik, "Malik was an expert critic of hadith; he knew it inside out as if he were sifting the pure gold from the fake". He rejected the doubtful transmissions and stuck to those which were well established.  I don't think we can go wrong by adhering to this principle. It would spare us from much confusion, especially when faced as we are with conflicting reports and opinions.

What we said above should is not intended to deny the great blessings of the month of Sha'ban. We know that the Prophet (peace be upon him) used to fast in the first half of Sha'ban, although he would refrain from fasting close to the month of Ramadhan so that its voluntary fasting is not confused with the obligatory fasting of the Ramadhan.

Furthermore, the Prophet was also in the habit of praying tahajjud as a regular habit throughout the year, including the month of Sha'ban. Allah knows best.