Let $B \subset \mathbb R^n$ be the unit ball. Consider a Borel measurable set $E \subset B$ with positive Lebesgue measure $|E|>0$ (say $|E| = |B|/2$).

Then, Lebesgue's density theorem, says that for a.e. $x\in E$ $$ \lim_{r \downarrow 0} \frac{|B(x,r)\backslash E|}{|B(x,r)|} = 0. $$

We can restate it as follows: for a.e. $x\in E$, for all $\epsilon>0$ there exists $r_0 = r_0(x, \epsilon)>0$ such that $$ |B(x,r)\backslash E| \leq \epsilon |B(x,r)|, \quad 0<r<r_0(x,\epsilon) . $$ I am particularly interested in the dependence $\epsilon(r, x)$.

I have a question about this. Probably it has been studied but I have not been able to find any reference.

Given $E$, can we prove some uniformity for $\epsilon$ in a positive measure set (maybe of measure smaller than $|E|$)? That is, can we find some $r_*>0$ and $\phi$ continuous with $\phi(0)=0$ such that $$ \epsilon(r,x) \leq \phi(r), \quad 0<r<r_* $$ for all $x \in \tilde E$ for some Borel set $\tilde E\subset E$ with $0<|\tilde E|\leq |E|$.

Edit: Initially I had two questions but I have decided to delete one.