Thanks!Sorry for the silence, Covid paid me a visit.
I honestly can’t tell how I would have read it spontaneously, but the suggested vocalization makes mor sense to me. موصول is a technical term in علم الحديث describing when a chain of transmission is uninterrupted all the way to the source (if memory serves), so it would make sense that it is here used as an adjective describing the أخبار
As for الإسناد بالإسناد it reminds me of this hadith:
لَتَتَّبِعُنَّ سَنَنَ مَن قَبْلَكُمْ شِبْرًا بشِبْرٍ، وَذِرَاعًا بذِرَاعٍ، حتَّى لو سَلَكُوا جُحْرَ ضَبٍّ لَسَلَكْتُمُوهُ، قُلْنَا: يا رَسُولَ اللَّهِ، اليَهُودَ وَالنَّصَارَى؟ قالَ: فَمَنْ؟
where شبرا بشبر, ذراعا بذراع means something like ’exactly’ ’painstakingly’ etc. so I think what is meant by مصولة الإسناد بالإسناد is that isnad after isnad, accounts of his noble character are constantly confirmed.
I'm not sure about the next bit, either:
وشهرت آثار كرمه شهرة واضحة الإشهاد
"and the reports of whose generosity have spread with a fame (or a spreading) clear 'in the calling to witness'" what does واضحة الإشهاد really mean? Something like "that can clearly (reliably?) be called to witness"?