另外一个问题是 可以混成 “思想想法” 吗？

不能，没有“思想想法”这个词

1. 他的想法很乱，一个点道理都没有。

另外一个问题是 可以混成用 “思想“和”想法” 吗？

我用得对吗下面这几个句子中，我是否正确使用了"思想"和“想法”？

1. 他的想法很乱，一个道理思维很混乱，一点逻辑都没有。

他一开口别人就会知道他没有好好准备这个报告。

2. 因为我和父母有代沟思想比较陈旧，所以我和他们有比较就的思想代沟。

（1）you should use 旧 here, instead of 久.

（2）因为我和父母有代沟，所以他们有比较旧的思想=> my parents have many old-fashioned thoughts because there is a generation gap between them and me.

I can not follow the logic in 因为我和父母有代沟，所以他们有比较旧的思想。

In Chinese, 代沟 refers to mentally generation gaps, for example, if your parents have many open thoughts and you can treat them as friends, you can say "我和父母没有代沟。"

I'd rather say 因为我父母思想比较陈旧/思想比较落后，所以我和他们有代沟。

（3）I think you can also use 想法here， like"我和父母有代沟，因为他们想法很落后"。

你们可以告诉我 “思想” 和 “想法” 的区别吗？

ism = 思想 [ similar feeling] --- a long run -- could effect behavior, directions and actions
idea = 想法 --- a short run --- coming out as a plan

For example
1.
伽利略的思想远远超越了他所处的时代。
Galileo's ideas were well in advance of the age in which he lived.


他认为他们可能用中产阶级思想去影响别人。
He thought they might infect others with their bourgeois ideas.

2.
我们不同的想法融合成一项计划。
Our different ideas fused into a plan.

这个想法遭到了各方人士的冷遇。
The idea met with a cool response from various quarters.

这两个词的意思是不是 “thoughts?"

thoughts n. 想法
thought v. 想... 事情 think...sth

另外一个问题是 可以混成 “思想想法” 吗？

I don't understand what you want to say
but those two words, for me as a Chinese reader, sounds strange.

1. 他的想法很乱，一个道理都没有。

I would I like to sound:
他的思绪很乱，毫无逻辑性。

他一开口就会知道他没有好好准备这个报告。

could be edit to be better.

2. 因为我和父母有代沟，所以他们有比较就的思想。

Because my parents and I have a generation gap, so they have a comparative idea.
that is what you said
little be weird.