Try to post pics without any oil coz of oil you hair is looking lot thinner
1) You are heading NW5.
2) May be or May not, Minoxidil works excellent on crown but try 5% Minoxidil as it is approved by FDA.I would avoid anything advertising itself as "10% minoxidil", since it hasn't been tested clinically.
Try Minoxidil for year and see whether its working or not!
3)There are many Vitamins Tablets available in market but don't expect full hair from it, it may help you to improve your hair quality.
some of Vitamins Supplements are - MSM, Flax Seed Oil, Dropped Nettle, Zinc100mg, etc the lists never end.
4) Why you not trying Fin? Dustasteride may help you to slow your hairloss and you need to be patient coz it may takes minimum 6 months or one year to see any results, Keep monitoring your hair
5) A top HT doctor may answer this question but I will say you can opt for HT, but don't expect drastic change. As you have hairline you may fill grafts on mid scalp and bit on vertex/crown and opt for buzz look.
Good luck