1) 2* farming isn’t something I’d worry about focusing on until you’ve got most 3s already championed. You’ve got several 3s at 13 covers just waiting for ISO to champion them; I’d definitely put your iso there instead of re-leveling 2s. The benefits of starting your 3 champion rewards is, in my opinion, greater than the benefits of farming 2s. For you specifically, you could probably sell your 2 Steve Rogers when he hits 144 and re-roster him at 15. Beter yet, roster one of the other 2s instead. He’s the worst 2 by a rather large margin (not counting Spider-Man) and you’ll get a nice boost of 65000 ISO and 125 HP for selling him at 144. Just don’t spend it leveling your new 2* Steve. (at this point, hands down spend it on a 3*)
1.5) At this point I wouldn’t be to fussed about rostering and leveling all the 2s. You’ve got some championed 3s already (9, it would seem) so a new 2* won’t help you out that much, aside from the eventual champion rewards, which are nice, but not as good as 3* champion rewards. If you find yourself at a point where you’ve championed all the 3s you can, and don’t have any other 3 with 13 covers, then sure, level up a 2* to 94 and champ them.
2) Stop opening legendary tokens (or spending CP on them). As you’ve noticed, single 4* covers aren’t helping you out right now, and single 5* covers can actively hurt you in many cases
2a) As a corollary to 2, don’t put any ISO into your 4s until you’ve got all your 3s championed. And don’t put any ISO into your 5s at all, for a really long time. You probably could have champed at least one of your 3s (if not 2 or 3) instead of getting that 1/1/1 Star-Lord up to 300.
3) If you’re not going to spend money on roster slots (totally legit) then you should probably consider selling those 4s with 1 or 2 covers. By the time you need them, they’re not actually all that rare (and you’ll have some legendary tokens and CP saved up to get a jump-start). Then roster all those 3s you’re waiting on, until you’ve gotten them all.
4) Don’t spend Hero Points on anything except roster slots. Can’t tell if you’re already doing this, but it’s worth mentioning. Everything you can buy with hero points, you can get for free eventually, except roster slots. Those will cost your 1000 HP apiece, forever. If you plan on rostering everyone then you will, as of this post, need 139 slots. 132 if you go the common route of ignoring every 1* except the one you use to do the first mission in the deadpool daily.
5) Do the deadpool daily. Again, can’t tell if you are or not, but do it 
You’ll miss out on Behemoth Burrito most of the time, but right now the CP you’d get from that you’d just be banking anyways (see #2). If you’ve rostered all the 3s, it’s a more or less free 3 cover every day, plus 2-3 taco tokens
6) Clear out the prologue. If you haven’t already. There’s a couple of hundred HP in there hidden behind Ragnarok.
7) If it bothers you that you have so many unusable 3* and 4* covers in your vine, hold off on opening tokens of any kind until you have enough HP to buy another slot. Then open tokens until you have to roster someone, or until you pull a 14th cover for someone who you could champion (if you had the ISO). Then stop immediately until you have enough HP for yet another slot.
I think that’s enough for now. Hopefully that’s all clear enough. They’re all just my opinions of course, although I think they’re pretty reasonable.
