I know you mention suggestions of not picking another team, but I just have to throw it out there that Titans for now very much is not a great defensive madden team IMO. And it seems offense to some extend is quite easier in M25, so you will obviously have some trouble on D, at least against okay madden players
1) With that being said, I personally would almost never run man coverage in 3-4. TEs already have an incredible easy time when covered by a LB, so often I would actually like to have a CB on their #1 TE (especially if he is a fast one). And if the other team comes out with minimum 3 WRs, then I will definitely never run man cov in 3-4 and let a LB cover an WR. I also refrain from cover 2 as well, as that often allows for an easy 10-20 yards on streak routes, and a TD if the safety on top is slow and bad at pursuit. When I man D, I often control the guy covering the HB, and manual cover him on his route (allows for quick reaction on screens too), and if he stays blocking you can use it as extra cover on middle or TE.
2) So far not much to do. It seems they made sacking numbers with only front 3 or 4 somewhat more "realistic" in numbers. So you now have to blitz to get fast pressure, and 3 or 4 mostly only works for coverage sacks. So if you dont have good coverage, 4 guys only will not get you many sacks. It is dangerous because it is a risk to send the blitz, can allow for a long TD over the middle in man cov blitz, and easy first down on zone blitz if read correctly. In online franchise you can kind of make the risk smaller by fx upping man cover on your safeties and stuff. I have yet to test it, but for online franchise you could probably also make a beasty DL to get good pressure without blitz. I had a 90+ str/spd/acc/power move DE in M13 which allowed for it, but yeah, dont know yet if it will work in M25
3) M25 seems to make user INTs drop more compared to M13, again probably to make it more "realistic" statistically. Not much to do then to keep trying for it. Even with good catching DBs like thomas, sherman and browner on hawks, they often drop picks
^all comments are just my personal opinion, but hope it maybe can help you