Best find a design professional that's familiar with the zoning in the City of Dallas. I'm working with a client that has a property right off Midway, north of Royal and is zoned R-16(a) and from the zoning chart, you can see pretty much what you can do. Although this zoning allows a 35' front set back, the original plat shows a 40' front set back so we have to use worse case. The 40' platted setback trumps the 35' city zoning. Building height varies by zoning. See the Zoning Chart
HERE. Now Dallas uses the "averaging method" meaning; take the distance from the highest ridge to the nearest eave and take that middle point. That point can not be any higher than what the zoning chart says. You can use
this map to locate your property by zooming up to it, then click the button above the map that says "Query a Point" then click the location your lot is. On the right a chart will appear with all the pertinent City Data including Zoning. It might say something like R-7.5(a), R-10(a) etc.. Then look to the chart for the requirements. You could enter your address and zip code on the left to find a property. If you do, don't enter the street type. Like for Lavendale Avenue, just enter "Lavendale" and not the Avenue, Street, Blvd, Road or whatever.
Good luck. If you need more information just PM me.