Regarding the exhaust cloud, when you look at that island, there is an area to the right of the track at the island level that may be exhaust, but it is well-hidden by the low cloud cover.
Once it leaves the ground, solid or liquid-fueled 1st Stages burn clean and bright. We are talking 500 feet of gas then nothing.
The pic is not great, but it looks like a ground or water-launched missile but not enough shown to evidence an arc that any missile usually takes when a ballistic trajectory
No as there are no radar transponders tuned to ADSB freqs. Plus, this is apparently a ballistic trajectory = mostly straight up, then a curve, then down, or up then boom to take out a flying target
That first stage is large enough to be a Titan III from a Nuke Sub. Likely source as I don't think any silos are near that Island.
Although I didn't track it, from memory, it seems that AF1 was not near the launch that I saw in terms of WhiteHouse.org flight path statements.
However, if it was a serious intercept launch, it can go a long way before it hits the ocean.
But, truly, they would have had to have some Surface to Air type weapon to hit AF1, and I am betting AF1 has serious countermeasure on board, let alone an escort. POTUS does not fly alone anywhere.
Sub type -
Definitely a Boomer, and an older one as the new ones do not have dive planes on the sail.
Only Ohio-class still has them. Sea Wolf and Virginia-class do not, I am almost positive