I agree with others that you really need to run your own numbers through one of many great calculators out there. I use the ones that Schwab and Fidelity have as well as a few others. You say you plan on retirement expenses of between $50-75K. That's a big range. Have you done an evaluation of your current expenses and projected those out to retirement when they will likely be significantly higher?
If you retire before 59.5 you will not have access to your retirement savings without paying a tax penalty. If you retire from the company where you have your 401k, there is a rule that allows you to withdraw if you retire after you turn 55 but there are restrictions on how you do this and it might require the option within your plan. You might want to check with your plan administrator and financial advisor on this.
I would strongly recommend that you have enough saved in cash or cash equivalents so that you can weather a down market without having to withdraw from your investments.
You indicated that you are renting with your mom (is she splitting the rent?) and that you get an additional $900 in monthly income from her and your two brothers. You might want to make sure to model your retirement numbers without these amounts as it is possible they won't always be there. For example, if the $900 a month is to cover your mother's living expense while she lives with you, what will happen if she needs to move to another facility like assisted living or eventually passes away? Will that income go away, affecting how much you have to live on now as well as in retirement?
Even if you opt to continue to rent, the amount will continue to go up. If you retire before 65, what will you do about health insurance until you qualify? You're happy with your car today, but you'll need to plan on replacing it over time. You need to include all of these things in your planning.
Good luck!