Math knowledge is very helpful, aspecially if you want to create custom movement and any other positional computations, as well as advance materials. UE4 can do a lot, but not everything, sometimes you need to go beyond borders. If you don’t have math skill, one day you might hit a wall and depend on work of others… which does not need to be bad thing, you can still make a game.
Web programming is little different expirance, unlike web where you generate text on http request, game is about updating state and generating frames in miliseconds, so you will need to switch some pipes in brain. C# and JAVA expirance will be useful, but SQL expirance might be useless here, you definitly won’t be able operate data in memory like that. The web skill overall can be useful if you want to create back-end for your game, also in UMG which layouting is kind of similar to Androids UI system, which is similar to HTML layouting.