MySQL table design / architecture, table is too big

I have a MySQL DB that contains a lot of text, I'm fetching data from a website and inserting it into a table.

I'm using a SSD HD (100GB) for the DB and I'm out of space, I think that something in the table structure made it too big, I can't predict the size of all the columns so I'm using varchar\text\medium text for most of the fields. when I insert all the data to the DB I monitor the errors and when I see that a certain field is too small for the data I'm trying to insert I'm increasing the size of the field (e.g. from varchar(1000) to varchar(2000)).

until now I have about 1.8M~ rows, I think that I'm doing something wrong.

here is the structure of my table –

CREATE TABLE `PT` (
  `patID` int(11) NOT NULL,
  `Title` varchar(450) DEFAULT NULL,
  `IssueDate` date DEFAULT NULL,
  `NoFullText` tinyint(1) DEFAULT NULL,
  `Abstract` text,
  `ForeignReferences` varchar(15000) DEFAULT NULL,
  `CurrentUSClass` varchar(2200) DEFAULT NULL,
  `OtherReferences` mediumtext,
  `ForeignPrio` varchar(900) DEFAULT NULL,
  `CurrentIntlClass` varchar(3000) DEFAULT NULL,
  `AppNum` varchar(45) DEFAULT NULL,
  `AppDate` date DEFAULT NULL,
  `Assignee` varchar(300) DEFAULT NULL,
  `Inventors` varchar(1500) DEFAULT NULL,
  `RelatedUSAppData` text,
  `PrimaryExaminer` varchar(100) DEFAULT NULL,
  `AssistantExaminer` varchar(100) DEFAULT NULL,
  `AttorneyOrAgent` varchar(300) DEFAULT NULL,
  `ReferencedBy` text,
  `AssigneeName` varchar(150) DEFAULT NULL,
  `AssigneeState` varchar(80) DEFAULT NULL,
  `AssigneeCity` varchar(150) DEFAULT NULL,
  `InventorsName` varchar(800) DEFAULT NULL,
  `InventorsState` varchar(300) DEFAULT NULL,
  `InventorsCity` varchar(800) DEFAULT NULL,
  `Claims` mediumtext,
  `Description` mediumtext,
  `InsertionTime` datetime NOT NULL,
  `LastUpdatedOn` datetime NOT NULL,
  PRIMARY KEY (`patID`),
  UNIQUE KEY `patID_UNIQUE` (`patID`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

what should I do? I have about 20% of the data (which means I'm going to need 350GB~ space) what is the performance impact here? should I divide the table into several tables over several HDs? I'm going to use sphinx to index and query the data in the end.

should I partition the table and use another disk for the partitioned table? will it help to create several tables out of this one? what would be the best way of doing so?

most of the queries will be SELECT, I'm going to search on about 4-5 text columns in this table (full text search + Sphinx).

Thanks!