PE12 video export quality

I spend a lot of time editing together home videos from source material that is a mixture of 1920x1080 .mts files at 25 fps and 1920x1080 .mp4 files at 30 fps.  I also include some stills (.jpg).

After trying many options I export the resulting single file to computer using the preset option for mpeg2 1920x1080i 30 fps, all done in Premiere Elements 12.

However the quality is always very disappointing, probably SD at best.  Before I upgrade to a newer version of PE, can someone tell me what I’m doing wrong or failing to do?  Or otherwise point me to a relevant discussion or article.