about 在这里做“关于”讲
TOM,an italian [about] whom little is known,saild into······
Tom,一个人们知之甚少的意大利人.
如果为了要体现出about的意思翻译这句话,就是
Tom,一个意大利人,[关于]他的事情只有很少被人知道.（这种说法有点别扭）.
italian后面是个定语从句
about whom little is known,whom代指an italian也就是Tom.
正常语序是：
people know little about whom(Tom).
人们对Tom了解很少.
alone 作单独讲,强调“仅仅这一个”.
These [alone] took sixteen months to build.
[单单]这个就花了16个月去建造
from 作“从...”讲
THE towers support the cables [from] which the bridge has been suspended.
塔楼支撑着吊索,大桥靠吊缆被悬挂着.
非要表达出“from”的话：
塔楼支撑着吊索,大桥[从]这里被悬起.
其中,cables（吊索）后面是一个定语从句：from which the bridge has been suspended.which指代the cables.
正常语序是：
the bridge has been suspended from which(the cables).
桥从吊索上被悬起.