Do contribute to the maximum allowable amount.

Because:
1) Your contribution is pre-tax. It reduces the tax you pay each year.
2) Company matching is free money. If you don't contribute above 7.5%, it's like throwing money away.
3) IRS has an annual cap of around $15,000 for 401(k) contribution. So you don't need to worry about over-contribution. It will automatically stop when it reaches the cap.
It looks like your company has a very generous plan. It's vested immediately and it matches up to 7.5%.