Doesn't look like anything that would be due to shade. It appears that the root system is insufficient to hold the tree up. This is highly likely to be due to improper planting (potbound roots, possibly internal to rootball, weren't properly addressed at planting). The only real "cure" would be to dig up the tree, bare-root it, address root issues, and replant. This would be a huge job compared to just planting a replacement tree, which is what I would recommend.

Hey Ken, Thanks for the response! I haven't pruned this tree save that one branch last year and some dead stuff, because I thought it ought to become established better before doing anything. If you can see all the old pruned branches, that wasn't me. You ask if I know how to prune... not by any of your standards, no. I've never been trained by anyone who knows a thing or two about trees - and that's why I'm here! The lowest branch is about 2.5-3' from the ground. The next (same side) somewhere around 4'. Obviously, they're too low, but there's a whole lot of foliage coming from those two branches and I'm hesitant to take them off. From what I understand I should have done it after bloom, but I really had no idea they would become that heavy. Silly me, yes. Please forgive my ineptitude. The stake was put in because the tree was side heavy and leaning even further under its own weight last year. I wanted to remove the lower branches, but hubby wouldn't let me. The stake is still supporting this weight (I tried earlier), obviously because the tree hasn't grown too much on the other side and the heavy side has just gotten heavier... I need to alleviate that weight, I assume. So, yes, please forgive this newb. I want to learn and understand, I really do.. it's just something I never make time for and, well, learning off the web is dubious at best. I'm attaching a few pictures below. Sorry I only attached the one last time. It was just because it only lets you do one and I had kids to tend to. :/

In ground, apparently you can dig a hole to uncover the roots to cause the plant to dry out and cause stress to make it flower, but its much easier in pots were you just dont water them Its that cold over here that ive not had a problem with the citrus flowering so ive not tried, but i do have a couple of bears lime trees that have flowered and fruited like a lemon tree , continuously flowered since last june under the growlights, i though they must have been lemontrees miss-labled but they are limes On other fruit trees such as pear,plum and apples it seems normal that if a few years after planting they havent flowered they chop the roots with a spade to stress the plant into flowering!, that sounds a bit drastic to me chopping the roots to cause a plant to flower

I've grown them successfully indoors. The pit that you take from a mango is actually a husk that contains a large flat fava bean shaped seed inside. Cut open the husk along it's edge, being mindful not to slice into the seed inside. I used a nail clipper. It was no easy task. After cutting all along the husk, I pried it open and removed the seed, I then layed the seed flat, a 1/2 inch deep in a large pot. I covered the whole pot in a clear plastic bag and placed the pot in a sunny window. Once it sprouted I removed the plastic and begin watering just enough to maintain evenly moist soil. Good luck