The weird branch could be a disease OR bad pruning.
I've had a tree pollarded. This is when you cut the branch way above the collar...it produces tons of shoots at the end. Maybe a previous owner did this to control the size. Looking closely I see what looks like a pruning cut.... The owner could have pruned it at a bad time, making it more likely to not recover. Maybe in Spring or Fall when the sap was running? If you
prune maples in summer, they will bleed less.
I have a feeling that the owner may have wanted a tree that looks like this one:
The marriage tree - Front Garden - Deb's Garden Blog You have to select a tree with a nice form from the get-go...or learn to prune like a japanese gardener and wait 10 years... It looks like your tree has TONS of branches (too many imo) in the middle, so you should be able to cut some of the hacked limbs back to right above the collar and the tree should be fine.
BTW also be ware of sunburn. You can cut some this year, some next year...some the year after that etc. If it is in full sun and you're in a hot area, you may also want to move it. Bulldog dad may be laughing now because when I joined the forum, I thought the Japanese maple that came with my house was a native RED MAPLE! ;D