Explanations:

I have 4 internet line of 2048/512, the internet service provider gives 10 valid IP by DHCP on each line.
I have connected one of the lines to ISA server and shared it among the users also there is VPN site to site on ISA server. Please note that we have DC which is used to define ISA policy.
There are also IP Camera, share point and video conference that need valid IP.

Enquiries:

1. Can I connect all 4 lines to Mikrotik to combine them? So for one user that is inside the LAN and behind the ISA server there would be 8 MB to receive?
2. If combination of the band width of download is possible then is it also possible to combine the upload band width? Can it combine that too so one user can enjoy the upload band width of 2 MB?
3. Is it possible to give valid IP to ISA server for VPN site to site?

I would appreciate if you could please answer my questions.