First, you should always put in more than a single DNS server or IP address. From the old DreamHost knowledgebase:
"First you'll need to login to your domain registrar (the company with whom you registered the domain.) You'll then need to change your domain's DNS settings so that your domain points to our servers. Our DNS settings are as follows:
Note that those are the IP addresses of the DreamHost DNS servers, and they are what you should be using, not the "22.214.171.124" ( that is the www IP listed under DNS settings in the DH control panel, and is subject to change at any time). All your registrar should need to know is how to "point" to the DreamHost DNS servers, and they should route the request to the appropriate DreamHost assigned IP address as necessary.
Nothing you put in the "root" folder as displayed by webFTP will be visible from the web, as that is the "user" folder beneath which any "sites" for that user are located.
You had the right idea by adding a directory/folder under that directory as your domain name (jonk.com.au), but the fact that you had to do that "manually" makes me think you missed a setup step.
When you "Add a Domain/Subdomain" to be hosted via the Control Panel -> Domains -> Manage domains screen of the control panel, it will create/assign a directory under your "user root" for the domain and associate that with your domain for the purpose of serving web pages for that domain.
Go to that control panel domain management page, and see if your "jonk.com.au" is listed there as a "fully hosted" domain. If it is not, click the "Add a New Domain/subdomain" link, and complete the provided form to "add" the domain to your hosting package. Note that you will have an opportunity on this form to define the directory that you want to be the "base" of that domain's pages.
If your domain is listed there, then click the "edit" button under the "web hosting" column for the domain, and confirm the directory setting previously mentioned accurately reflects the directory in which you are storing the files to be servd over the web.
You can use either SSI (.shtml) or PHP based includes on DreamHost. SSI instructions are available on the DreamHost wiki (http://wiki.dreamhost.com/SSI), and there are many tutorials on how to use PHP to include other files.
If you want to use SSI with .html files (instead of with .shtml files) you will need to make allowances for that as discussed in this DH Wiki "How can I use ssi on files with .html extensions".
Sure, just use .htaccess to set it up - there are lots of examples of how to do that on the web and/or in the DH Wiki.
The DH Wiki has a lot of very useful information about this and many other DreamHost related tings, and you should explore it a bit to see what is there.
Just a though here: If you have unrelated/different questions in the future, it is more helpful to other users of these forums if you post each question as a separate post with a descriptive title that describes the subject. This makes it easier for those browsing the forums (for information or to offer help) to identify a post in which they are interested or for which they can provide help, and makes it easier for subsequent visitors to track the answers that are given for a particular subject. Oh yeah, and "Welcome to DreamHost".