Welcome to the Wonderful World of Kitten Parenting!
My advice: Go get a second one *NOW*
Cats do not take up really any room except for thier litter boxes and food bowls. So even in limitted space, it's the perfect situation. They don't become as big as dogs and such. Hehe. I tell you to get a second because I know from experience that a solo-cat can easily get depressed, despondant, and lonesome if alone for too much. Boo was very lonely until we got Drizzle. Problem is, if you wait and get a second later, they'll be **** to pay for the first weeks. Hissing, scratching, biting, growling, true fighting. Right now your little Tobey still remembers his Brothers and Sisters. If you grab another cat now, integration should be a peice of cake! Get another one his age, though. Maybe go back to the same litter/place you got Tobey from?
Really, two is better than one for a multitude of reasons, not the least of which is they keep one another always company. You are Tobey's world, so when your not home, he's got nothing, really. Another cat will give him a pal, a brother/sister, someone to be there so niether is ever alone. And the sooner, the easier it'll be to get them together. Every day you wait he's forgetting what it's like to be with other cats.
Now as babies, when they play - which looks to us like fighting - they might go a bit too far, so you must watch them closely at first and if they look to be hurting either one, break um up. They're like kids. Hehe. But most of the time the "fighting" is in truth playing. It's cute. Hehe.
Trust me. Two cats are best if your not home too much. You both work, yes? Not home for much of the day, like most folks? Go grab a second kitten.
The added cost of food/litter is negligable, truly. Shots/Nuetering is the only thing you must worry about, cost-wise. But that's (shots) a once a year thing and neutering a one-time only.
As to hieghts too high for him to jump too/from: don't worry. He'll get the hang of it. He's a baby, he's learning. When my guy was a baby (8 weeks old when I got him) he did the same things. So help him out. Lift him to places he wants to go. If you see him about to jump down, help him down. This will slow him down in jumping too/from places. Then, when he's older and lager, he'll be more prepared physically for it. I did this with Drizzle, and he's turned out Puuuurfect. Hehe. He waited for me to place him places as a baby, and then about 2-3 months began to jump on his own. But it gave him time to grow if you serve as an elevator. LOL.
Sneezing: He may have a cold. Feel his nose. Is it wet? If so, don't worry. Cat's get colds a lot. It should go away soon. If it persists (beyond 3-4 days) then you might want to get concerned. But cats are on the floor a lot, in colder spots, blah blah, and more suseptable. Also, he may have an alergy. Nose could be wet from sneezing from that too. I know Drizzle sneezes at dust. But after a while, he learns where dusty places are, and avoids them. So will Tobey.
Always purring is... well, pretty normal for a baby in my experience. Only had one, granted, my Drizzle man, I wasn't around for Boo's baby time, but he was ALWAYS purring. It'll decrease as he gets older to the point he only purrs when being/wanting love and sleepy. It's ok, though.
Like I said: Cats don't take up any space. Get a second. Think of it this way: your buying a new Shoe, a new Microwave, and two new peices of China. LOL. Same size as a new Cat, new Litter Box, and new Bowls. That's the size requirements of space for a cat. Even the smallest place can manage two. Hehe. Believe me.
Sooner the better, for them both, so they'll remember being with other cats from thier bros/sisters.