Sorry while it makes sense in a way for years I had nothing wider than 35mm but I didn't get anything wider until recently when I got 28mm as part of the deal with my zoom ... there was no alternative. 28-280 is what came
NO instead of getting a wide-angle lens I learnt to stitch two or more frames together with the immediate result I had more pixels for detail and didn't waste a third to half on my existing pixels on sky and foreground when I wanted the wide view.
So I suggest you use that 35mm ... it is not ideal and preferably you use a 50mm or more but it saves money and is viable.
Plus no way do you need a tripod and I have done dozens of wide views hand-held ... it does of course mean you need a good or proper editor which has layers and IMO that is a far better investment than a good wide lens
edit .. reading back I see Dave also suggested stitching and do not be put off by the nay-sayers who say stitching is limited, as you get more experience you will find that is far from true if you use an editor a I do rather than one of the myriead of stitching programmes.
So to your #7 I would ask do you have a good editor with layers? You have already spent enough on gear so is time to spend a bit on the 'equal partner' to your camera. Personally I have used Paint Shop Pro for around a decade now and it is not too expensive while in its clunky way the free download Paint Dot Net is quite capable ... but how much of that is my experience with PSP and lateral thinking when I don't find the tool or variant I want I really do not know
Another thing you do not need and that is a polarizing filter as these are a strict NO-NO with stitched shots and even wide-angle lens ...
Have fun and try my idea before you spend money ... that is the DSLR disease that afflicts most people here because they have an ILC. I largely cured myself of that in my early digital days by using a bridge camera and now with an ILC I am aware of the suseptiblity of the ILC owner