T2 was my first pin and when I put in my LED's over half of them didn't work. So I feel your pain. For the wedge type connectors, the LED's use a single wire for each side of the wedge. On the original bulbs the wires are loops which creates more contact area. For mine, I had to remove each LED and spread the wires to form a "V". This gives it more surface area horizontally. Sometimes you have to adjust the wires a few times to get a good contact.

I run the playfields all the time when I have them lifted to troubleshoot. For T2, the arm to prop it up doesn't lift it very high. I use an old crutch to prop it up so I can get better access to the bottom of the playfield.

To reflow I would first just reheat the existing solder. Keep it simple first.

By the way, if you do prop up the playfield higher than normal, take the balls out first

I believe mine moves slightly to the right before going left so I think you're ok.

For the drop target, you are talking about the one in the skull right? I took mine out to put on a new decal and it went pretty easy. Finding something to prop up the playfied is key.