I'm touched by how big your heart is for your dog. It's always a really hard time for owners and families when they know that "time" for their beloved pet is approaching.
Regarding the seizure activity: unfortunately, without diagnostics, it can be hard to figure out why a dog is having seizures. It could be a number of things: masses/lesions/tumors in the brain or brain stem, chemical imbalances, epilepsy, genetic conditions, hypoglycemia, and any other complication or infection involving the brain, spinal cord, and nervous system. It's also not uncommon for dogs to have what are sometimes called "geriatric seizures" - just because they're older.
There are medications to help manage seizures (Phenobarbital, Keppra, Potassium Bromide, etc), but these are literally impossible to get without a veterinarian's assessment and treatment plan. They can manage seizures and maintain quality of life, but they can get expensive.
For Rowdy, I can't think of any homeopathic or "natural" remedies. Sometimes seizures are caused by hypoglycemia, or low levels of sugar in the blood. Sugar water would help your dog if his seizures were caused by the hypoglycemia, but I doubt that's his underlying issue, because of his age and otherwise good health.
My advice would be to keep doing what you're doing. I would obviously recommend getting some testing done, even seeing a neurologist for diagnostics and maintenance medication - but due to his age and your financial situation, that's probably not an option. So just keep up the good work. He may continue to have seizures (likely), but just try to be there for him when he does. Talk him through the seizures; sometimes you can rub their eyes and it calms them down a bit (do NOT put your hand anywhere near his mouth, as sometimes they can bite without realizing it).
The important thing for you and Rowdy is, like you said, quality of life. If his seizures progress - occurring more often and lasting longer -- it may be getting close to his "time." If he can't enjoy his favorite activities, can't get up and walk around, doesn't feel like eating, drinking, and doesn't even get up to go the bathroom, it's time. If his seizures interfere with daily life, it's time.
I hate to be the bearer of bad news, but he is an older dog, and it's something that will happen within the next couple of years or so. In the meantime, spend as much quality time as possible while you still have your best friend around.
Good luck with Rowdy !
