Choose N pairs of (job, time slot) with a constraint on the number of different jobs
The last constraint is also no problem. You already have variables $x_{j,t}$, that say if the person works the $j$th job on the time slot $t$. Now you can introduce new binary variables $y_j$, that represent, if the person works at the job $j$ or not. Then you can model the constraint by:

$$\sum_{j \in J} y_j \le 2$$

The only part left is how you connect the information from the $x_{j,t}$ with $y_j$. But that is also not hard. If any of the $x_{j,t}$ is $1$, then you can force $y_j$ to also be $1$ with the constraints

$$y_j \ge x_{j,t}\qquad\forall t \in T, \forall j \in J$$

and force $y_j$ to $0$ if all $x_{j,t}$ are $0$. This can be done with:

$$y_j \le \sum_{t \in T} x_{j,t}\qquad\forall j \in J$$