It looks like many of those buds are still viable, so I doubt you have too much to worry about.

The most important factor to consider when growing a JM in a container is the quality of the potting medium. The potting medium needs to be of a very high quality - durable yet freely draining. Rather than going into all the details now, I'd suggest you research the forum archives about growing JM's in containers or check out the Container Gardening forum for helpful posts on potting soils. Of especial interest would be a recurring thread on that forum about growing trees in containers.

Since I can't see either the soil or the size of the container in the photos, I can't comment on how appropriate they might be. I'd caution you to opt for a larger container rather than a smaller one - if you are using a high quality potting soil, then excess soil surrounding the rootball is not a worry and you also won't need to root prune or repot as frequently.

Anything in a container will need routine fertilizing as well. I dose all my containered JM's with a slow release pelletized fert (Osmocote) whenever I pot up and at the start of the growing season and that typically will take them through the summer. I will also sometimes use a water soluble fertilizer to supplement if the summer is dry enough or hot enough to prompt heavy watering. This is because every time you water a container grown plant you pull out or leach some of the nutrients from the soil and these must be replaced for strong health growth.

So if you pay careful attention to 1) the potting soil, 2) proper fertilization and 3) adequate watering/irrigation, you should do well with growing your JM's in a container.

PS. please do not shorten the name to "jap" - that is considered a pejorative term and has the potential to be insulting. If you need to abbreviate, JH is the accepted terminology or just spell out Japanese maple. Thx