Your 401k yearly max contribution is 17.5k and you are contributing $1,425 a year (28.5k x 0.05) with your current salary. At your income bracket, I wouldn't worry too much about trying to bring down your taxable income that much for tax purposes because you are at the lower end of the bracket (not trying to offend, just stating a fact).
So, if you are truly going to end up with around 15k in cash, stick it in the bank and for gods sakes DON'T TOUCH IT. That is your 6 month emergency fund. Next you need to work on bringing your expenses down to a minimum. I wouldn't change your 401k contribution until you have 9-12 months earnings in that account.
Once you have a budget and your 9-12 month emergency funds in place, you can look at bumping up your contribution. I would suggest bumping it up to 10% and seeing how that's goes. My % goes up every year when I get a raise, if I get a 4% raise all 4% goes into my 401k, I'm getting pretty close to the max contribution now and I'm only 34. You also should open a Roth IRA and contribute any bonus money or tax refunds or any other windfalls into this account, you can put up to 5500 a year in here and it's tax free to pull the money out when your retire.
You just have to get disciplined about it. I didn't get serious about things until I was 30. Admittedly when I was 30 I was in a better financial situation than you, but its all about perspective. The same principles apply whether you make 20k or 200k
I would also say that you should be taking advantage of any and all tax credits possible because you should qualify for basically everything. You aren't doing yourself any favors if you leave anything on the table, the government isn't going to do anything useful with it, I can assure you of that. When you get to the higher end brackets, they take 90% of deductions and credits away and just stick their hand out and tell you to pay up.