@Linze Peters I hope I am not being rude here. I have a development and construction company and used unlicensed subs a lot of times when I know the quality of their work.
With the 30k budget, it is doable for touch up and re-sand/paint projects without major changes (depends on sqft as well). You may need to organize the subs and hunt for your own subs (of course depending on how much work you need). However, as a GC, I don't think a qualify GC will do the job for $30k (maybe a 1-2 men crew when they do everything by themselves). Right now the labor market is fairly competitive with a shortage of qualify subs.
With that being said, here is my advice on your answers and I hope that helps. Maybe others can say otherwise.
1) I don't trust any of my subs right the way. I would ask for minimum of 3 bids for each trade. Each of them will have different advice and pricing and you take the best pick.
2) Yes it is worth it times to times, you get what you paid for. I have a tile guy who charges just the same as a big company but I know he is doing great work. I am keeping him
3)You are most likely looking for a contractor/subcontractor. Interior designer designs your house not actually getting the job done.
4) I would refer to yelp to all the inspection services, as I find most inspection services reliable as long as they got good reviews.