Why can't I repeat the verb with degree complement in “昨晚我的朋友表达得很明确”?

Question

I thought I have finally been able to wrap my head around this structure, but it seems no, not really.

So I have seen this sentence:

昨晚我的朋友_表达_得很明确。

But according to my native speaker friend, you cannot say:

昨晚我的朋友_表达表_得很明确。

However, he also said you can make the following sentence:

昨晚我的朋友_表达_意思_表达_得很明确。

My thinking was that verb repeating kicks in when there is an object, but then he made this sentence:

昨晚我的朋友_讲话讲_得很明确。

Hence my questions:

1. Does this mismatch come from the fact that 表达 is just a verb, while 讲话 is technically a verb + object, just like 游泳，吃饭，放假 etc.?
2. Can I just say _表达_意思_表 without repeating the 达 part, as in 他_讲课讲_得好, 每年冬天我们_放假放_三个星期 etc.?

Answer 1

1. Yes. 表达 isn't a VO, it can't be split like you're trying to split it.

2. No. 表 isn't used by itself as a verb like that.

Also you could just opt for something much simpler like: 已经说得很清楚, rather than the mouthful that your current sentence would become.