My thesis advisor is absent in my final stage of completing my Ph.D. programme I am a mathematics Ph.D. student who are in my final stage of completing my Ph.D. programme. My advisor is visiting an institute for a few months. The institute that he is visiting is in another country; because of the visa requirements and many other practical reasons, I cannot go there with him.

Now my progress is, I have all the main results ready (most of them have been written down) and I need to finish writing my thesis in about three weeks. My advisor has guided my through all the mathematical difficulties; now he left me behind to write the thesis all by my own. Furthermore, he has clearly indicated that he will NOT help me with the writing process. 

Now I need to figure out many things all by myself, from LaTeX to the organization, from the usage of languages to drawing pictures, etc. Also I need to verify the correctness and validity of all the results; he mentioned that he will not carefully read my draft. And I do not have much time to finish everything. I am feeling somewhat stressed and overwhelming. 

In this situation, should I seek assistance from other professors/lecturers who do research in a similar field, or should I try to figure everything out by myself? Should I hire someone to proofread my thesis when the draft is finished?
You are about to finish a PhD thesis. Somebody who obtained a PhD title is supposed to be able to organize and conduct reasonable projects independently. I think that your adviser is not being unreasonable in his demands.

Part of organization is also arranging to get more time, if your current time frame cannot be kept, or leads to serious degradation in quality and rigorousness. In some cases that might lead to working on your thesis without being funded. Personally, I would still advise to value doing a good job higher than meeting a deadline, but of course I cannot oversee all the consequences.