Hadith on staying awake on the nights of Eid

Q:

عَنْ أَبِي أُمَامَةَ رضي الله عنه عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ : (مَنْ قَامَ لَيْلَتَيْ الْعِيدَيْنِ مُحْتَسِبًا لِلَّهِ لَمْ يَمُتْ قَلْبُهُ يَوْمَ تَمُوتُ الْقُلُوبُ رواه ابن ماجة

Is this Hadith correct? Can we attribute it to the Nabi (sallallahu alaihi wasallam)?

Repenting for one's past sins

Q: I have a personally sensitive issue. When I was a teenager, I engaged in inappropriate sexual touching with a few girls one of whom was my cousin while she was sleeping. Now that I'm an adult and a bit wiser, I feel terribly guilty. I have apologized to my cousin but without telling her what I did. How can I find peace?

Second jamaat in the musjid

Q: If due to rain in certain parts of the world, Maghrib and Isha’ are prayed together in the masjid. Would it be permissible for Hanafis to conduct a second congregational Isha’ prayer in that masjid, because it is forbidden to conduct second congregation prayer in a masjid?