I'm not sure how long your long runs are but if they're shorter than 26.2 you're probably not going to finish a marathon on it. Limping or otherwise. Injuries like this need only one thing and that's rest. Good news (from my experience) is your calf strain is the quickest one to heal. Here's what you can do.
No running for another 7 days.
Get on Aleve. 2 tablets in the AM with food. 2 tablets at night with food.
Keep the calf wrapped.
When possible keep it elevated above your heart.
I'll call this ICE (ice, compress, elevate)
Ice it 3 times a day. 20 minutes on ice. 5 minutes off ice. 20 minutes back on ice.
After 3 days of this you need to do some deep hard massage. You need to find exactly where the injury is located and take both your thumbs and press deep and hard at that location and surrounding areas. A golf ball works well also. I usually massage until my hands can't take any more. Ice immediately after using usual ice routine. The next day your calf should be sore as hell. Time to add stretching. Search the web for good calf stretches. There are a ton.
Keep the ICE routing going.
After a week of ICE head to your local track. With your calf wrapped tightly walk a lap. If it feels good jog the straight and walk the curves. When jogging if you feel anything in the calf discontinue the workout and ice and stretch. If you can jog w/o discomfort continue the jog/walk until you feel the slightest discomfort or 8 laps. Ice and stretch when done and keep up with the wrap, elevation and ice.
Rest the next next doing the same ICE and stretch routine.
Back to the track after the rest day. Same routine and conditions. If no discomfort continue for 12 laps. Ice and stretch when done.
Rest the next day. You should be around March 7th at this point. All running going forward should be w/o the calf wrap. If you feel anything in the calf you need to stop running and head home. After every workout you need to stretch and ice.
Here is how I would recommend you run until your marathon.
3/7 Run 5 minutes, walk 2 minutes for 4 miles
3/9 Run 8 minutes, walk 2 minutes for 4 miles
3/11 Run 4 miles
3/12 Run 4 miles
3/14 Run 6 miles
3/17 Run 10 miles
If you can finish the 10 miler w/o any problem you may make it. I would run the marathon with the calf wrapped. Good luck.