There are tall growing varieties and there are not so tall growing ones. Probably your best course of action is to let it grow as tall as possible to get a thickened trunk then cut it very low. That way you should get a number of side shoots/branches. If you cut it early with a thin trunk you're likely to get fewer branches. Having it up against a fence reduces the area branches have to spread out and is what promotes a taller tree. If you had a grafted tree those don't grow as tall as the ungrafted ones.

The mango won't worry whether you're 16 or 160, it'll still be the same. The advantage is you wouldn't be too old by the time a seed grown tree produced fruit. But yes, prices on trees do vary a lot depending on where you live. The difficulty though with seed grown trees is they take so long to mature and then you could easily end up with fruit you don't like. There is however another option and that's grafting a tree yourself. Not the easiest thing to do but there's a lot of advice available on the internet. You can start off with a seed grown tree, doesn't need to be very old, and you get a piece from an older tree of a variety you like. The piece from the older tree is called "scion wood". The scion is as old as the parent tree and so is able to produce fruit very early, and it's identical to the parent tree fruit. You can get scion wood by asking around on forums, there's always people who are willing to share a piece of their mature trees. There are also places that sell scion wood but try freebies first. For germinating seeds, the husk isn't a problem. The important thing is to keep up the warmth and to not let them dry out, that's what convinces the seed to start germinating - the tropical conditions you create. The big 'but' here is that you have viable seed. If you can't be sure the fruit hasn't been chilled or had something done that kills the seed then ask if someone can send you some seed. I would but I'm not in the US so quarantine would confiscate it before it got to you. You've started on the path already, and there's a bit of a way to go yet. But it's very doable. Just keep asking questions along the way.

color of flesh can vary with sun of course and as you may know all mango trees blossomed out of season this year in south florida so i wouldnt judge it on that. my little 3 foot julie mango tree dropped its ripe first mango last week. i planted it about 8 months ago. Graham is a seedling of Julie so it may be identical, im not sure how mango trees seeds inherit traits, does it have to do with cross pollination of another variety or is it just a crap shoot like passive recessive genes in humans? either way i guess the best way to find out would be to hunt down a ripe Graham mango and directly compare them.

I have been searching for info on mango espalier in the internet and I found a pdf document which has complete details about how to grow/harvest/prune short(truly short), healthy mango trees in the ground. Yes...in the ground. Since the tress are going to be really short, we can easily put a tarp on the top during winter freeze etc. I believe, the entire process is doable even by any amateur gardener like me. The document is from John Yoshimi Yonemoto, Japan Tropical Fruit Association. The entire document, I would say, is equivalent to taking a university course in the topic and thanks for their generosity in publishing the document. I am so.....motivated to start few mango trees in our yard. My best wishes to all the mango lovers who dream of having mango trees in their yards irrespective of their zone. Here is the link. http://hawaiifruit.net/PruningYonemoto.pdf