Story time.
Thank you Emma P for proofreading!
Notes
1. 少林狮吼功 an actual technique said to be part of "Shaolin's Seventy Two Secret Skills". It has been variably recorded as the cry Siddharta Gautama emitted at birth to claim his dominion over the Earth.
2. 世兄 lit. "brother of this world". Refers to somebody who's a friend of the family.
3. 沈慎 lit. "liquid caution". Shen Shen is also a homophone of, funnily enough, "auntie". 蜀中 (Shuzhong) refers to the ancient state of Shu, and is situated in the central regions of nowadays Sichuan.
4. Respectively:
江南张家: Zhangs, near Suzhou
太湖赵家: Zhaos, near Taihu Lake
洞庭高家: Gaos, in Hunan
蜀中沈家: Shens, in Sichuan
太行陆家: Lus, near Taihang Mountain
I'll make a map of this for fun.
5. 华房龄 lit. "belongs to the rich house". Pretty literal name.
6. 礼记 by Confucius.
7. 容炫 lit. "holds awesomeness". Very "hero-sounding" name. Titular character of the chapter.
8. 匹夫无罪，怀璧其罪 lit. "although an innocent man, possessing precious jade made them guilty". Either refers to arousing covetousness from possessing something precious, or arousing envy by being extraordinary.
9. 封山剑 translated literally.
10. 武功心法 lit. "kung-fu heart method". In context, it is a text that elaborates on topics "at the heart" of kung-fu practice - a.k.a key elements. In Buddhism, a 心法 refers to a religious text that teaches the faith/philosophy but isn't sutras.
11. In the text, he is said to have 走火入魔 or "walked into the fire and entered the deviant/devilish way". 走火入魔 is a milestone of kung-fu gone wrong. Variably translated as "entering the demonic path" with differing level of "satanism" or magic involved depending on the context, the phrase actually can describe anyone who becomes obsessed with something to the point of deviating from the norm. Here it is used to imply that Rong Xuan became weird all of a sudden presumably due to his kung-fu practice.
12. ZZS teaches the boy 口诀 (lit. "mouth trick"). 口诀 are precepts or instructions on a given subject that are versified/rendered in chants or rhymes for ease of memorisation. Recitation is traditionally a big thing in Chinese education, much more so than in western education. From a very young age, schoolkids are trained to recite poems at an increasing level of difficulty. Scholars in ancient times are often said to know whole books by heart.
13. 解释就是掩饰，掩饰就是错误的开始 translated literally. To my knowledge, a modern humorous colloquial phrase.