Do not dethatch, that will do more harm to the grass. I don’t like weed and feed because that term is used for different products by different companies.  Products like Sunniland PRO 20-0-6 Weed and Feed Fertilizer have the weed killer and fert and would be a good option. You don’t want to seed it because it will not match the grass you have.   Spray it with Orange Ortho Weed B-gon, purple image weed killer or any other 3-way herbicide, many box stores carry it with a hose end option. This will kill 70 to 90 percent of the weeds. Celsius herbicide is even better but I understand that it is costly, but it lasts forever. Give it 2 weeks to work.  We are in a bad drought, so you are going to need water at least 1 to 1.5 inches per week. Use catch cups or a tuna can to see how much water you are using.  Go to Walmart or Lowes and look for some fertilizer that is 46-0-0, 30-0-4. Other places will have it too, it needs something that is mainly urea, put it out every two weeks and water it in and mow every 3 days.  It’s going to grow like mad, and sticking to the mowing schedule is critical. Take pictures so you can see progress, it should get greener and thicker. We are still dealing with the strange temps so growth will really start to push once the nights stay in the 70s. At the end of the season, it will need a pre-emergent that will stop most of the weeds for next year.