Hey and welcome
DO not sweat your pack. It sounds large enough to hold yer stuff. After you get some experience and the other gear, then you can consider a diferent pack. You may find that with some experience, that you have a better idea of what has to go into your pack. Most of us feel that the pack is the single most important piece of gear and should be bought last.
Ignore anyone who says your "pack is too big", or that smaller is better. A pack has to be big enough to hold your gear, you can go smaller/lighter later. Personally I carry a 6500" pack. I Have never felt that it was "too large". Unless you have a really modern down UL sleeping bag and squeeze the heck out of it, it won't even fit into a mini pack.
Get your sleeping bag/pad together and work on clothes. You can shop for camping clothes at Goodwill. When I was a poor hippy backpacker I wore levis and tee shirts. When you need either some skills or better equipment is when the weather turns fowl.
You said that you have a tent. If you put your tent and sleepng bag into your pack, how much room is left? Enough for a coat, food, cook gear, rain gear, sleeping pad etc. Try this out before you go selling your old pack.
As far as going solo - a lot of more experienced peops prefer it, but you're better off having someone to teach you some skills first. Often its the unknown elements that can get ya. The stuff that ya simpley don't watch out for cause you haven't been hurt by it yet. Its like hiking in a desert if you're used to forest - different things will get you than what you are on the look out for.
A friend is a good thing, as long as they are as sane as you are. If you go with a friend, try to share your gear so that you each carry less.
DO NOT overdo the safety gear and what if stuff. I mean yes take the ten essentials , but people carry way too much un-needed junk, and a 5 pound first aid kit, bowie knife, axe, spare clothes, cooking flies, ground clothes, spare stoves, extra pans, and lanterns are not required for most trips. My combined gear is light not because the individual pieces are light, but because I simply do not carry a lot of it.
Another falacy - layering is not always the best way to go, it depends. Layering clothes is heavy, but works well for the money if your gear isn't highly specialized. A down jacket to wear in camp could
be much lighter than sweaters and more layers, and warmer. You will have to learn what works for you in the places that you go.