You need to assist the site in draining to a different location (underground trenches and pipe) or you need to substantially raise the planting beds. We recently had to do this to our front yard, prior to our landscape renovation project coming up this fall. Once the pipe was properly installed, the front yard went from a mire after a heavy rain to absolutely perfect! And we have heavy clay soil. It's a do it yourself job if you know what you're doing. Here is a link that might be useful: drainage construction

Letting the trunk move with the breezes will do the most to strengthen it. It was grown in a crowded nursery plot, and tied up to get the maximum height - which came at the expense of width. It WILL make up for this, but be careful in your tie-ing. If it is too loose, it may break at the tie in a very strong wind, and if it is too tight, it won't move enough. As well, as it thickens, you need to loosen the ties so it can continue to move. Using 2 or 3 ties would be better than a single tie - the wind-forces are better balanced. If you search, you should get several discussions of tree ties/supports and how to arrange them. Fertilizing, as long as the tree is planted in reasonably decent soil, will do little to help. Watering the tree as it needs moisture will be the most help, after careful monitoring of the ties.

Thanks gardengal48 for the info! I had a look at the 2018 prices for JM at a large nursery half an hour away from me. Yikes! I hadn't looked at JM prices in ages. Now I wish I had picked up another $6 one. And actually my husband and I (at the same sale) were deciding on whether to purchase a $40 red dissectum JM (named, but don't remember now). It looked really nice. Didn't purchase it because I figured I had a lot of learning to do regarding container trees and didn't want to kill it. Should have snatched it up then and there! It was the only one left. Darn!!! Oh well. But now I am more knowledgeable thanks to you all!

i have a red flowering chestnut.. that has had a similar.. though larger .. wound for 15 years now .... tree time as i call it ... the vascular system of the tree is the cambian layer .. which is just under unaffected bark ... so in theory.. the tree can live a long time ... interior wood is ... simply put.. the structure that holds the tree up .... what i figure is that... especially on my 15 foot tree ... is that as the tree gets bigger every year.. eventually ... probably in some wind storm ... the STRUCTURE of the tree is just going to collapse.. there just wont be the interior structure to hold it up .... especially when the wind blows ... and its leafed out ... the only reason to cut it down .. is to watch how it might respond ... thats how most of us.. had to learn.. before the WWW ... part of the learning curve.. you might say... but i have 5 acres.. and lots of space for this type of experiments .... most people dont have spare space ... frankly.. its all down to whether its bugging the beegeebees out of you .. and whether you would be better off putting it out of your misery .... its not like its hanging over your bedroom.. and going to crush you in your sleep some night ... ken