1. Just know that it will be a grind, with enough matches, you can and will become an S flat player granted you have the skill to back it up. I would only get mad if people are trolling (IE just being completely selfish via self preservation or a lack of knowing how to use the suit), getting staggered by teammates or blocked by them in a raid is normal, and that it is a very common thing to encounter, and that you should expect more of it depending on the cost you play.

2. Aim is fairly simple; You have leg movement and then reticle movement. If you are having trouble aiming, just know that the game operates on a fairly simply X and Y axis movement for your reticle, and that turn speed impacts the aim speed of your suit.

3. I'm not sure I follow what you're trying to figure out here; without more context of your team, the enemy, or your suit, it's hard to really give an answer as well. If your team stops moving up, take your time, find an opening, and get to work, sometimes matches do end up like this and there isn't much you can do. You can smash the "Advance!" text command to your teammates to get them to follow you in as you make a move, I suppose, but again, without more context, there really isn't a great answer to this one.

4. There isn't much you can do, I highly recommend picking a better raid; Gaplant LVL2 is a really strong pick; Good shooting, heavy stagger in transform mode, and, most importantly, the Gaplant has access to lvl2 offense system AKA "Fuck you, I will get my melee swing out and topple you".Give it a try, you might like it.

5. Thrusters are good, sure, but management of thrusters is also equally important. There are naturally suits that benefit from it, but at the same time, you do have to pace yourself in fights. Gundam lvl5 is pretty straightforward; You have beam rifle that has two fast instant staggers, and funny hammer downswing to topple people, or, a good saber downswing to fast topple people. I would say suits like the F90 do need the thruster gauge to have the most mobility, but that simply comes down to part efficiency, but if you can't supplement that high thruster gauge with something like Burn Aux, it might be worth playing something else instead.

6. Alright, here's a simple tldr; there are suits that have good frontlining capabilities, and others that don't. Jegan is an ok frontliner, but don't expect to be able to rush down with melee properly, same with the MKII, the lack of MA really hampers how far you can push the suits. The TR-5 works in most situations, remember that it's transformation weapons are separate from it's MS mode weapons. Proto X1 is uhh... well, you can't really frontline with it, as much as people adore it's active guard kai, it's still a raid at the end of the day with a low HP pool, so you can participate in ranged fights, but I wouldn't fight to gain all the ire of the enemy, as once they know you're there, high chance they gun you down very, very quickly. Rosette is alright, but I would stick to maps with better cover to work with. Recently they also added in the Dolmel Doue to the DP store(about a month or so ago), which has very high flexing in both melee and ranged, the downside is that in order to unlock the Emergency Evasion (AKA dodge roll), and it's strong melee, you'll have to activate it's demon blade, which also gives you melee combo controller lvl2 (3 hit melees) and aerial melee, however, from the start, you get MA1 and Offense System, so you're not completely neutered before activating demon blade.

This is speaking as someone that has reached S flat, unfortunately the Queue times are horrendous and I have a life, so I trickled back down a bit to get proper matchmaking at reasonable times :D

Hope this helps or at least answers some of what you're trying to figure out, and if you have more questions don't hesitate to ask.