Hi Chelsea, welcome to the forum!
It sounds like you really have your hands full with Ollie. How long have you had him? What have you tried so far?
Potty training:
Neutering does make a huge difference in marking, but at the end of the day, marking is a potty training problem. Re-teach potty training from the beginning. Assume your dog has a two-hour bladder and walk him at those intervals, even if you "know" that he can hold it longer than that. The potty training stage is the worst time to gamble on anything -- if you catch yourself using the word "probably" (as in "he probably won't pee"), you're gambling. Potty training is a game of habit formation. You want it to become so firmly entrenched that it's almost superstitious: the BEST place to go potty is outside, and therefore the ONLY place to go potty is outside. Every time he is allowed to go inside, that habit is weakened.
If your eyes aren't on him, he needs to be crated (contained somewhere he would never pee, not even once). In the beginning, it means a lot of restriction on the dog's freedom and frequent potty walks, but it's worth it in a few weeks when your house doesn't smell like urine anymore and it ultimately improves his quality of life.
Investing in a belly band/male diaper is worth the $15 to keep the urine off your objects during the training process. An enzymatic cleaner like Nature's Miracle will help to get the smell out so that it doesn't keep triggering him to pee in the places where he has already peed.
You'll also want to get some type of treat container to store near the door you exit for potty walks. Grab some treats on your way out the door and always have them in your pocket when you and Ollie are outside. If he potties outside, make it very exciting and happy, hand him several of his favorite treats all in a row (I'm talking good stinky meaty treats, not just milkbones), make it like winning the puppy lottery every time he pees outside.
If he pees inside, don't fuss at him. You run the risk of him associating you watching him pee with punishment which makes leash training unnecessarily complicated, and it doesn't actually teach him what to do. So it doesn't help, and it may hurt.
It's hard to keep a level head when the dog has just peed on your belongings, and it's very human to feel frustrated about it. It's natural to want to shout or fuss or scold the dog for peeing inside, to show him what he did wrong and to vent your frustration. I've been a dog trainer for years and I still struggle with that with my own dogs (although not with clients' dogs). Personally, I've found that making a deal with myself is really helpful. As long as I don't ever lie to myself that I'm "teaching" the dog anything with it, I'm allowed to yell. Which means that before I open my mouth, I have to consciously acknowledge that I am just yelling at my dog because I'm upset, not because I'm training him or because it's his fault -- that I'm just shouting at him because I can't contain my anger, and it won't accomplish anything except making me feel less angry. And nobody wants to be the mom who shouts at her kids/dogs for no reason when she gets frustrated. So, even when I desperately want to shout, that's how I trick myself into not doing it. Might help if you are also the easily-frustrated sort.
The big secret to potty training is that it's actually pretty easy if you follow the rules all the time, and it's almost impossible if you don't. The rules are:
1. Prevent accidents indoors before they happen, and
2. Give plenty of chances to potty in the right place, and
3. Heavily reward potty in the right place
That's the whole thing. The rest of it is just tips and tricks to make that process go more smoothly.
Obedience:
1. Make your idea pay off better than his idea.
2. Teach him what you want in the least-distracting, smallest-length-of-time, easiest way you possibly can. Then reward like crazy as soon as he does it. For teaching "stay," this means one-second stays in a completely silent boring room (bathrooms are great for this) and he gets a fantastic treat every time he does it.
3. Reward generously, often, and as close to immediately after the behavior as possible. If you haven't already, looking into clicker training would be a good idea.
While at work:
1. Put him in a crate.
It sounds like you would really benefit from a book on dog training. Dr. Sophia Yin's "Perfect Puppy in Seven Days" would be a great place to start -- it answers all of these questions in much more detail than I've given you and it gives you a really good foundation in dog training. It's written conversationally and it's a pleasant read.