2012 Yaris SE

[D-Flo]

I'm thinking about exercising my purchase option at the end of my 3.5yr lease (should be a little over $9,000 w/ approx. 42K miles). But I have a few questions:
1. Interior dash and side panel plastic. This seems to scuff and get dusty very easily. IS there a recommended cloth or cleaning solution for this plastic which features a texture consisting of tightly-spaced shallow parallel grooves (the dust catches in these grooves)?
2. front and rear bumper panels - seam separating. Is this an easy fix? The plastic tabs don't seem to grip onto each other, making the seams look unkempt.
3. I've got 1 more scheduled maintenance before decision time on the purchase. I want to save a little $ versus going to the dealer for service. I'm supposed to use ILSAC multigrade engine oil at 5W-30 viscosity. Does this mean I must purchase synthetic oil? Are there non-synthetic standard motor oils out there that meet the ILSAC standard?