1. This is the routine my mother and I perform every Sunday when we can purchase one drink and get another free, and always with a shared smile.

2. Dancers and choreographers seem to have the toughest time of it, earning the worst pay and with the least education.

3. I have watched, very carefully and with great respect, the theory and practice of selling satisfaction and serving millions of people on a daily basis, successfully.

1. 首先要说明的是，不同的词或短语，如果它们的句法功能是相同的，就完全可以并列。如下面的句子，and连接的是副词和介词短语，但它们的句法功能是相同的（即都是用作状语）：

He stood up slowly and with difficulty. 他缓慢而艰难地站了起来。

She solved the problem carefully and without error. 她细心而准确无误地解决了这个问题。

She answered the question concisely and without mistakes. 她简要无误地回答了问题。

The eagle attacked quickly and with great force. 那只鹰迅速而强有力地发起了攻击。

He answered all their questions very easily and without hesitating. 他轻轻松公且毫不犹疑地回答了他们的所有问题。

2. 在你的三个句子中，第二、三句比较好理解，下面分析一下第一句：

This is the routine my mother and I perform every Sunday when we can purchase one drink and get another free, and always with a shared smile.

分析：本句的and并非连接两个状语，其实and后面可视为一个省略句，相当于and always do this with a shared smile。也就是说，这个and其实连接的是三个动词短语purchase one drink, get another free, always with a shared smile。省略后的and…成分起补充说明作用。另外，句中的 free 是副词，它不是宾语，而是状语（=免费地），get another free=get another drink free（再免费获得一杯饮料），即 another 后面省略了 drink，这种省略属于“承前省略”（目的是为了避免重复）。