1. Is it even worth it right now to start mining after thr crypto values falling down? and if it is, is it still profitable to mine with cards lower than 1060 or 570?
I think it's not worth it to buy lower than 1060 or rx570 I suggest that you buy rx 570 because ethereum mining still profitable and stable and I think you must use whattomine.com as a calculator so that you can calculate how much you can mine daily or monthly the profit will be still depends how you sold your coins if you sell them in right time then you can make a high profit.
2. If i pay my rig with a 1-year installment (using my mining money + my monthly income) will it be risky considering the GPU durability? I'm afraid that my mining GPUs don't last over 1 year.
I think it still worth it and we don't know how long the durability of any GPU but don't worry I think there is 2 years warranty or 1-year warranty of all GPU 's then you can send it back to the manufacturer.