First of all, downtown D is pretty safe these days, especially when there is an event going on. There are lots of bars and restaurants scattered all around from the Greektown Casino, The Old Shillelagh is a great local bar, The Detroiter Bar is a classic dive bar (just like the ones in Blo), The Roof Detroit is just across the from Comerica Park, Detroit Beer Company is a brewery on Broadway....lots of choices. Corktown just a mile west of the downtown on Michigan Avenue (too far to walk, Uber there) also has many bars and restaurants, like Nemos (a great Detroit tradition, dating back to when the Tigers played at Tiger Stadium), Slows BBQ, Lager House, etc.
Walking around going from place to place is no problem, no worries there. I was just at the Sabres/Bruins game and frankly, the D has many, many more options for downtown restaurants and drinking than Blo.
Tailgating is not like at the Bills games. There is tailgating, just different cause the parking is in small downtown lots. So space is VERY limited in the lots, so you don't see a lot of huge tents set up because the parking lot owners want paying cars instead of tents. And it will be expensive to park close to Ford Fiels, like $40 -50 or so. A lot of tailgaters just open up the back and stand around. Lastly, the old thing about alcohol not being allowed was gone years ago. Everyone parties just like anywhere else. Good luck, have fun in the D, I'll be there and Go Bills!!