You seem to have done your part, from how you describe it, and have a right to expect that they know their role in this relationship.
Theoretically both employees and employers would want the company to prosper and have a future, each side must do their part.
As an interviewee your main duty is to yourself, as an interviewer the main duty is to the company (though the interviewer might also wish to advance their own career, improve their resume for future employment).
Deciding how much the company pays you is not your job, you don't even work there. If advertising and interviewing is what the company does then arguably they are doing their job, otherwise they need to have something on the table too.
If you have nothing on the table then it's a waste of time for both you and the company, but a paycheck for the interviewer. If the company doesn't have enough on the table then you are willing to subsidize the difference or are wasting your time.
When your resume is poor, new, or you're 'vacation working' (studying options, planning to leave for various reasons, learning something interesting regardless of the compensation) then you probably want to comply to the extent that you want to work there.
If you are in the better position and they are stalling when asked about how they will perform their half of the agreement it's a red flag that either they have financial shortcomings (be it cash available or willingness to part with it) or shirk their responsibilities.
Your current benefit is that you've gained some more experience interviewing (as has the interviewer and possibly the company, in their policy about fair dealings with people) and should choose to cut your loses (spend no more time and money) in a polite and professional manner - should they discover that everyone else feels the same they may come back to you with a reasonable written Offer Letter.
Messing with people who are on a fishing expedition, who simply like to advertise repeatedly until they obtain compliance, who can do their end, or are financially stressed should lead you to question the longevity of the position, or even the company should they find no one.
The awkwardness is their defense mechanism, a compliance test at your expense, or a one sided thinking. If they've nothing to offer at this time welcome them to contact you in the future.
You could have been hired sooner for equal or better pay if they (whomever) could see how you would be of value, no company with work and money throws both work and money away because they have too much (expansion issues aside) only places who mess around throw away what little they have and the work that would come with competent and loyal employees.
Decline politely to do more until they've demonstrated their interest. You do not ask how much money the owner gets or what the profit is during the interview and so it's not their business to ask how much you made previously, how much you paid for School, your shirt, your home.
Wages are their part, they are defensive because that's always been their shortcoming, that and doing their end (part) when called upon. I would have had an idea about wages before I invested my time but you should stick with your guns and show your commitment by doing only your own job (unless you get to set the wages and make the hiring decision for them too).
Deal with people politely and efficiency unless you're a hostage negotiator (too many interviews with too many people - a sheep fishing expedition).