Not the optimum plan for your time in Chengdu, and while you said you have 5 days, you have only outlined 4 days and that’s a big difference. While most of what you have can be rescrambled and fit in, Day 2 is particularly problematic with Emeishan. While it’s true that Leshan and Emeishan are only about an hour-ish apart by road, Emeishan at a minimum needs a full day on its own, and most people do an overnight and most of two days, especially if wanting to see a variety of areas on the mountain. However, in January it will definitely be miserably cold all over Emeishan and the summit may be too snowy to physically access or too foggy to visually access. I therefore suggest that you reconsider this, and skip it unless you have a 5th day. With a 5th day and high speed rail access now available, it’s acceptable to do a trip there and return to Chengdu since you’ve already prepaid for your Chengdu hotel, then return to Leshan another day. Leshan can be done in a half-day round trip from Chengdu.

Without the 5th day and assuming only 4 usable days and no Emeishan, I would rearrange as follows, with days 2-4 pretty interchangeable:
Day 1: City stuff. What you have is fine.
Day 2: Pandas in the morning, Sanxingdui in the midday/early afternoon, maybe Baoguang Temple on the way back to Chengdu.
Day 3: Leshan in the morning, maybe Huanglongxi or other old town in the afternoon (or other city sights).
Day 4: Dujiangyan in the morning, should be able to fit Jinsha Museum on the way back to Chengdu, or if you are museum’ed out, proceed back to Chengdu city for other sights in the afternoon. I do like Wenshu Temple and area surrounding it, and would not miss it. There’s also an interesting City water ecological park not too far away from Wenshu.

If Emeishan is something you really want to do, then I’d cut Sanxingdui due to geography, and take a join-in tour on Day 2 to Pandas in the morning and Leshan in the afternoon. Usually these are cheapest if you go through one of the hostels like Mix or Sim’s (even if not staying there). Since they may not be offered daily, whichever of your Days 2-4 do this tour, that’s when you’d do it. Then what was Day 3 above would be put to Emeishan which you can do yourself by high speed train—take the earliest one out and then and then a late afternoon or early evening train back, and do some research so you know in advance what your Emeishan internal route content will be.