No, I would not switch out the flooring. The AO tile is not cream, it's a warm white. The difference may be subtle but an offwhite/white color scheme is beautiful if planned from the beginning and is rather difficult to do well and not look like you got a bargain on mix and match fixtures and tile. Go the distance with your original plans and it will all be fine. If anything I might consider going with a different color than ultra-white on the walls. Maybe a soft grey or sage green or aqua or something.

Perhaps the easy one?

Photos would help us help you. However, in general, if you tend to like neutral rooms but feel a need for a bit of color without going too bright, you can always use a toned down color in your accessories (pillows, table/wall decor, rugs, etc.). That way, you still get the soothing simplicity of the neutral colors you enjoy with a little interesting touch. Another safe and effective way of adding color is by simply adding greenery to a neutral room. In my experience, a few green plants are exactly what a neutral room needs to liven it up a bit.

Miracle Gro is a perfectly adequate fertilizer and should work well. No need to change it up midseason...it works from planting through to harvest. 5G is a pretty small container for an indeterminate like German Striped. I'd recommend a 15-20G container. If you leave it in that size, you will be watering a lot more frequently and therefore need to fertilize a lot more frequently. Half strength at least weekly or with every other watering.