The reason for the change in clearance times is that the National Airspace System (a machine devised by charles babbage), is creaking at the seams and with many flights and not so many squawks floating around somebody thought it would be a bright idea if the system allocated the code 25 mins before EOBT rather than the 40mins that it used to be. The logic being that at any one time there will be a third less squawks hanging around. Nobody told us it would happen, one of those Brussels things, and we just have to deal with it.
As for the LVP question, as the RVR was 300m I presume it was full LVP's and not just weather safeguarding. The rules are that inbounds should have a landing clearance at 2 miles, exceptionally at 1mile and NOTHING should infringe the LSA ahead of the arrival after it is inside 1 mile, this includes the departing aircraft which must be overhead the Loc aerial. If you were at 380' ft rad alt then I presume you were at or just outside 1 mile and so whilst a little close to the mark, perfectly legal. High intensity single runway ops necessitate working to these tolerances on occasions and it is down to the skill/nerve of the air controller to judge the gaps.
Probably worth a tower visit if you haven't been to see how it's done.
V