The Scottish NHS has always been separate, but Wales' has diverged since devolution. The east of Wales has a long border with England... The north east is near Liverpool so a lot of people travel there for major services. Some people in the far south of Scotland go to Carlisle in England for maternity services etc but this is less common.
For all practical purposes Westminster is also the English Assembly, so there is no reason to believe a putative devolved English Assembly would have decided otherwise. Now, a devolved Northern English Assembly, that would be far more interesting.
Sort of but then you have the west lothian question, about Scottish or Welsh MPs voting on English issues. For instance these MPs should never have voted on student loans
Devolution came about because of the reverse. Parts of Wales were flooded to provide England with water, which destroyed Treweryn and other communities... All but one Welsh MP voted against that. There were many times during the 1980s and even when Margaret Thatcher introduced legislation that was unpopular in Scotland. The Poll Tax was the culmination of this, and was imposed on Scotland before anywhere in the UK.
England can outvote Scotland, Wales and Northern Ireland's MPs combined so the West Lothian Question is not as big of an issue for England as the reverse.