I am working on online resources for PhD students. Please share any such resources you have come across. Preferably free resources!

I would personally recommend Ulatus. One of my fellow Phd colleague had mentioned about it. - https://www.ulatus.com/

I would suggest that the best way forward is to connect with other PIs from your university (or to approach staff members/career counselling professionals from your university) and ask them for specific feedback on your application. The other suggestion would be to get in touch with hiring managers at companies. Although they may not always be receptive, some would definitely share pointers with you and suggest ways to make your future applications more robust. There have been instances where rejected candidates have approached the interviewing panel for suggestions and successfully secured jobs after incorporating these constructive suggestions.

Although the current job market is not in a great state, it is never difficult to get a job in the industry of your choice, provided recruiters/hiring managers find your CV attractive. Always remember not to underestimate your skills. Keep looking for opportunities even in some of the lesser known companies, as they tend to recruit personnel with broader or slightly non-specific skill sets. A few high-profile companies also do the same. Have you attended any good conference lately? Are you making a conscious effort to network with peers and influencers from your field? Do you have an up-to-date LinkedIn profile? You can check out this useful resource I came across that offers important tips to postdoctoral researchers: https://www.enago.com/academy/top-5-career-tips-ph-d-postdoctoral-researchers/

I am really sorry to hear about your rejection. I would recommend not taking such comments personally. If you have not received any positive comments from the reviewer feedbacks, then try to find out what the reviewers have actually suggested. Consider it as a fantastic opportunity to add value to your research and to your future thesis. i. We must always welcome feedback, as long as it is constructive. On a related note, most reviewers (at least those associated with good journals) tend to share legitimate input. You can also try asking your peers to go through your paper and share feedback with you. Making the necessary changes and submitting to another journal would be the other possible option. But under no condition should you let this affect your physical or mental health.

I am really sorry to hear about your situation. However, if you have made the necessary changes to your research proposal/synopsis/thesis based on the feedback given to you by your examiners, then you should not have an issue in passing your viva the second time. You can consider this as a positive improvement to your research proposal/synopsis/thesis, which will only benefit you as an author and as a continually evolving researcher.

I would recommend you to check popular sites like ResearchGate, Nature, and Science for postdoc positions first. Apart from these, you can also check some of the other websites listed below:

http://www.scientifica.uk.com/research-jobs
https://www.postdocjobs.com
https://www.eurosciencejobs.com
http://academicjobs.wikia.com/wiki/Academic_Jobs_Wiki

Furthermore, make sure you visit the webpages of promising mentors that interest you, and write to them directly. This works very well quite often!

Well, there is no particular age limit to start a Ph.D. course. Quite recently, someone started pursuing a Ph.D. at the age of 66 (http://www.sciencemag.org/careers/2018/07/its-never-too-late-stretch-your-wings-why-i-got-phd-age-66). All the best to you feel free to reach out if you need any help!

There are a number of software tools available for creating poster presentations. However, it depends completely on the type of content being presented. Most often, PowerPoint seems to be the default standard among most people. However, there are some other tools like Adobe Illustrator, Adobe InDesign, Corel, Microsoft Publisher, Inkscape, etc. that can be used to accomplish this task. You may also experiment a bit with Canva or Visme, although mostly for scientific illustrations or flowcharts.
Following are the links to these tools -

https://www.adobe.com/in/products/illustrator.html
https://www.coreldraw.com/en/
https://inkscape.org/en/
https://www.adobe.com/in/products/indesign.html
https://www.canva.com
https://www.visme.co/

It seems that you are confused between a literature survey and a PhD thesis. The standard procedure involves conducting a thorough literature survey in your field to identify a problem. Once you identify the research gap or research problem, you propose a research question. You then have to find novel solutions to address your research question. In order to accomplish this, you need to carry out well-designed experiments that would help you find the answers. At times, the actual outcome of your experiments may not necessarily match with those predicted initially, but you should nevertheless report these in your research paper/thesis. Hope this clarifies your doubt.