Actually, (1) can be written two ways, depending on the idea to be communicated. If he is insisting to others that Tom is careful, the sentence would be: He insists that Tom is careful. If he is to force Tom to be careful, talking to Tom, or talking to others to see that they require that Tom do things carefully, the sentence would be: He insists that Tom be careful. 2. Actually, this could be said: It's a great pity that she is so careless ( she is careless all the time, or often) It's a great pity that she should be so careless ( A single incident happened in which she was careless.) You might also hear this last one as: It's a great pity that she was so careless.

fdmaxey has explained it nicely. Just know that when we want someone to do something, we use the subjunctive. However when we use "is" in the first sentence or "was"/"is" in the second sentence, we want to talk about permanent characteristics of that person.

i find this in a grammer book .

Did your teacher give you this, or did you find it online? I have a feeling that your English needs to improve before you can comprehend this type of grammar.