Is this jacket warm enough for winter?

No. It is an unlined stretch canvas shell with no insulation, so it works as a mid-layer or a mild-weather outer layer. Add a fleece or hoodie underneath in cold weather.

Does the DWR treatment make it waterproof?

It is water-repellent, not waterproof. Light rain and splashes bead off, but sustained rain will soak through the fabric and seams.

How does it fit compared with a standard work jacket?

It is cut relaxed and boxy, with more room through the body and sleeves than a trim-fitting chore jacket. That makes layering easy; size down if you want a closer fit.

Is it tough enough for real construction work?

It handles light yard and shop work, but the stretch canvas is lighter than heavy duck canvas. For daily abrasive jobsite use, a heavier traditional work jacket holds up better.

How should I wash it to keep the water repellency?

Wash cold and tumble low or hang dry. Heat and repeated washing wear down the DWR finish, so reapply a spray-on DWR treatment when water stops beading.